E V Five A Electronics World 1967 07

User Manual: E-V Five-A

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Electronics lIb i ld
STATIC ELECTRICITY -The Space Age's

Billion- Year -Old Gremlin

ELECTRONIC CHALLENGES IN SUPERSONIC JET PROGRAM

PROBLEMS AHEAD FOR TV TECHNICIANS

Integrated Circuits Will Force Major Changes

SPICSs
IOUS

TRANSISTOR

66.1

0-13IJONIdS
C100MN11

3 47ZLZ

NyWONIH

.:SOW-147ZLZNIHOOL47IS 69SOM

4.**ACiirt.4;

When we put this
four layer voice coil
in the new E -V FIVE -A
we knew it would
sound better...

we never dreamed

it would lower
your cost of stereo
by $9400, too!
The voice coil is the heart of any speaker.
A coil of wire. It moves the cone that makes the
music. And in most speakers, that's all it does.
But in the new E -V FIVE -A we've found a way to
make this little coil of wire much more useful.
Instead of one or two layers of wire, we wind the
E -V FIVE-A woofer coil four layers deep.
Voila!
Now the coil actually lowers the natural
resonance of the 10" E -V FIVE -A woofer. And
lower resonance means deeper bass with
any acoustic suspension system.
In addition, with more turns of wire in the
magnetic field, efficiency goes up. But it goes up
faster for middle frequencies than for lows. This
means we must reduce the amount of expensive
magnet if we are to maintain flat response.
It's an ingenious approach to woofer design, and
it works. E -V engineers point out that their efforts
not only resulted in better sound, but also cut
$47.00 from the price of the E -V FIVE -A.
So now you can compare the $88.00
E -V FIVE -A with speakers costing up to $135.00
... and come out $94.00 ahead in the bargain
for a stereo pair! The difference can buy a lot of
Tschaikovsky, or Vivaldi, or even Stan Getz.
And after all, more music for your
money is at the heart of high fidelity!
Hear the E -V FIVE -A at leading audio
showrooms everywhere. Or write for
your free copy of the complete ElectroVoice high fidelity catalog. It is filled
with unusual values in speakers, systems,
and solid -state electronics.
P.S. If you think the E -V FIVE -A
woofer is advanced -you should hear the
tweeter. But that's another story.

high fidelity systemsand speakers tuners, amplifiers, receivers public address loudspeakers

microphones

phonograph needles and cartridges orgars

space and defense electronics
410

ELECTRO- VOICE, INC., Dept. 774N, 629 Cecil Street, Buchanan, Michigan 49107.
CIRCLE NO. 111 ON READER SERVICE CARD

OICC

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Don't move a muscle!
This security system is so sensitive, it can be
adjusted to detect the motion of your arm turning
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And if this Portable Model Unit were within 35 feet
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it can detect fire... turn on lights... even notify police.
What does a burglar alarm have to do with you?
Just this: Radar Sentry is no ordinary alarm. It is
the most modern and effective security system available. And it's also electronic.
That's why we need you. We need Dealers with
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It's been proven time after time. In fact, many of
the more than one thousand readers of electronics
magazines who became Dealers in the past year
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And that's why we need men with technical knowledge and experience.
Men like you.

July, 7967

CIRCLE NO.

t04

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How about it?
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22003 Harper Ave., St. Clair Shores, Michigan 48080

Please tell me how can have a business
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Systems. understand there is no obligation.
I

Nanne

Address
EW -7

City

State & Code

ON REAIDER SERVICE CARD
7

ANY GOOD CARTRIDGE WILL TRACK THESE 7-ASSAGES

BUT ONLY
A HIGH

TRACKABILITY
CARTRIDGE
CAN COPE
WITH THIS
GROOVE!

CLOSE THE TRACKABILITY GAP
(AND YOU'LL HEAR THE DIFFERENCE)
The photomicrograph above portrays an errant, hard -totrack castanet sound in an otherwise conservatively modulated recording. The somewhat more heavily modulated
grooves shown below are an exhilarating combination of
flutes and maracas with a low frequency rhythm complement from a recording cut at sufficiently high velocity to
deliver precise and definitive intonation, full dynamic
range, and optimum signal -to -noise ratio. Neither situation is a rarity, far from it. They are the very essence of
today's highest fidelity recordings. But when played with
an ordinary "good" quality cartridge, the stylus invariably
loses contact with these demanding grooves -the casta-

nets sound raspy, while the flute and maracas sound
fuzzy, leaden, and "torn apart." Increasing tracking weight
to force the stylus to stay in the groove will literally shave
off the groove walls. Only the High Trackability V -15
Type Il Super -Track® cartridge will consistently and effectively track all the grooves in today's recordings at record saving less- than -one -gram pressure ... even with cymbals,
orchestral bells, and other difficult to track instruments. It
will preserve the fidelity and reduce distortion from all
your records, old and new. Not so surprisingly, every
independent expert and authority who tested the Super
Track agrees.

SI--IVRE
SUPER TRACKABILITY PHONO CARTRIDGE
At $67.50, your best investment in upgrading your entire music system.
Send for a list of

Difficult -to -Track records, and detailed Trackability story: Shure Brothers, Inc.,
CIRCLE NO. 102 ON READER SERVICE CARD

222 Hartrey Ave

Evanston, Illinois 60204
© 1967 Shure Brothers Inc.

ELECTRONICS WORLD

pec(robiesAolq

Electronics World
JULY 1967

VOL. 78, No.

CONTENTS
this month
symbolizes our special issue on "Transistors." We
have shown four interesting
and colorful photomicroOUR

COVER

graphs of some of the newer transistor structures. The
circular photomicrograph is
that of a Motorola selective metal -etch high- frequency

germanium transistor.
Above- and to the right is

Static Electricity: The Space Age's Billion- Year -Old Gremlin

24
26
28
30

Recent Developments in Electronics

Solid -State Circuit Breaker Operates Within Microseconds

32
34

Independence Hall Reconstruction Sound System

Electronic Challenges in the

SST

Program

One -Tube Low- Frequency Converter

rrrI

H. su./

Electronic Stethoscope & Cardiac Rate Meter

Troubleshooting Integrated Circuits
Part 1. The Functional Approach

w. Thoma,

H. We,, k, Jr.

W3T1Q
A.

Dues.

Waller H. Buch5boum

Peter Nelson
&

William D. Hr:nn

Siliconix diffused epitaxial
junction field -effect transistor. Below and to the right
is an RCA "overlay" high
frequency power- transistor.
The photomicrograph at the
lower left is of a. Fairchild
MOS field -effect transistor.
Our background for these
photomicrographs consists
of a grouping of the new, inexpensive plastic (epoxy)
packaged transistors from
General Electric, Motorola,
RCA, and Siliconix.

SPECIAL

37
38

44
45
49
52
53
56
57

60
60

SECTION: TRANSISTORS

Selection of Transistors R. M. Rydor
Small - Signal High- Frequency Transistors
Diffused Transistors Jac i Ha. race
Alloy Transistors
Power Transistors Ronald W. va
Field- Effect Transistors Allar D. E.ans
The Unijunction Transistor
Small -Signal Low- Frequency Transistors
Resonant -Gate Transistor
Switching Transistors sh Fi..rro
High -Voltage Transistors
How Many Transistors?

T. J. Robe

66
77

Neutralizing the Cascode Amplifier

EW Lab Tested

Lse

Richard A. sfaciar

Bishop

Solid -State Image Scanner

.e
J67i'iÜ

Bogen TR -100X Stereo Receiver
Wharfedale W20 Speaker System

l'nLlishrr
PHILLIP T. HEFFERNAN

62
72

WM. A. STOCKLIN

Technical Editor
S.

John Frye

Test Equipment Product Report
Fairchild Model 7050 Digital Voltmeter
Bird Model 6155 R.F. Wattmeter
Lafayette 995065 Volt -Ohm- Milliammeter

Editor
MILTON

Ham Radio and Semiconductors

SNITZER

.Issoria/i' Eillira.
LESLIE SOLOMON
P. B. HOEFER

,i.,.aistant Edilnr
MARSHA JACOBS
Contributing F,ditor.,
WALTER H. BUCHSBAUM
Prof. ARTHUR H. SEIDMAN
Ist l'alilor
HERBERT L. SILBERMANN
.1st and Drat ling Dept.
J. A. GOLANEK
.Idreriising unles Rlandger
LAWRENCE SPORN

Adrerti.uing Neuire Manager
ARDYS C. MORAN

July, 1967

MONTHLY FEATURES
4

Coming Next Month

Radio & TV News

Letters from Our Readers

New Products & Literature

Book Reviews

Electronics World: Published monthly by Ziff -Davis Publishing Company at 307 North Michigan Ave.. Chicago.
Illinois 60601. One year subscription $6.00. Second Class Postage paid at Chicago. Illinois and at additional
mailing offices. Subscription service: Portland Place, Boulder. Colorado 80302.
All rights reserved.
Copyright

1967 by Ziff -Davis Publishing Company.

PRESENTS...
The IDEAL Amplifier

COMING
NEXT
MONTH

I:Ivei io»ies \1udtl

SPECIAL FEATURE ARTICLES ON:

SA30 -30

AUDIO
TAPE
RECORDING

Audio Tape Recording

.11i11

Two timely articles of interest to audiophiles and professional sound

men will cover
Selecting the Right Tape by Joseph Kempler of Audio Devices and Biasing in Magnetic Tape
Recorders by John G. McKnight of Ampex. The audio tape article provides up -to -the minute
information on the many varieties of tape available, including the cartridge units which are
becoming so popular in both car and home. Also covered are valuable hints on recording
so as to avoid print- through and distortion, along with proper storage methods to preserve
valuable recordings. The article on biasing includes practical information on the biasing
circuits used in home and professional tape recorders. The effect of various amounts of
bias current is discussed along with the pro's and con's of different biasing schemes and
freq uencies.

Over 60 watts of dynamite
Clean Transparent Sound

Military -Grade Parts,
Workmanship & Reliability
Only 1 -3/4" thin, 19" rack
mount

Price $19900
For complete characteristics and

specifications write for Bulletin
114, or ask any proud owner.

VALUE ENGINEERING FOR
THE ELECTRONICS INDUSTRY

management philosophy of applying a
forced organized approach to reducing
costs while maintaining product quality
is discussed in detail by Fred H. Possner,
Director of Value Engineering at Airborne Instruments Labs. Striking examples of the efficacy of this approach are
included.
A

CATV: PAST, PRESENT

& FUTURE

Jerry Hastings of Jerrold's CATV Division provides a comprehensive report on

the current status of community antenna
television systems and their potential in
the near and distant future.
THE OPERATIONAL AMPLIFIER:
CIRCUITS & APPLICATIONS

An in -depth discussion of these highly
versatile controllable -gain modular or IC
packages which have been widely used
in computer and military circuits in the

past but are now appearing in commercial and consumer products. New price
and size reductions should stimulate use.

All these and many more interesting and informative articles will be yours
ELECTRONICS WORLD . . on sale July 20th.

in the August issue of

ZIFF-DAVIS PUBLISHING COMPANY
William

Ziff
Chairman of the Board (1946 -1953)
William Ziff
B.

President

Editorial and Executive Offices
One Park Avenue
New York, New York 10016
NEW YORK OFFICE
James J. Sullivan
Joseph E. Halloran

W. Bradford Briggs

Executive Vice President
Hershel B. Sarbin

Senior Vice President
Philip Sine

Financial Vice President
MODEL

1/4

SX124

ONLY $995

Walter S. Mills, Jr.
Vice President, Circulation
Stanley R. Greenfield
Vice President, Marketing
Phillip T. Heffernan
Vice President, Electronics Division

TRACK STEREO

Modular Transport
Low-Noise Circuitry
Third Head Monitoring
World's Finest Recording Quality
Speed

Response

7-1/2

±2db 30 to 25,000
±2db 30 to 15,000

3-3/4

S/N
55db
50db

Gsay- zurr., International
BOX 1000, DEPT. EW -7
ELKHART, INDIANA
MADE ONLY IN AMERICA
CIRCLE NO. 97 ON READER SERVICE CARD
4

Frank Pomerantz

Vice President, Creative Services
Arthur W. Butzow
Vice President, Production
Edward D. Muhlfeld
Vice President, Aviation Division
Irwin Robinson
Vice President, Travel Division

212 679 -7200

MIDWESTERN OFFICE
307 North Michigan Avenue
Chicago, Illinois 60601
312 726 -0892
Midwestern Advertising Manager, Royce Richard
WESTERN OFFICE
9025 Wilshire Boulevard

Beverly Hills, California 90211
213 CRestview 4 -0265; BRadshaw 2 -1161
Western Advertising Manager, Bud Dean
JAPAN
James Yogi

Ichikawa Mansion
Sakuragaoka
Shibuya -ku, Tokyo
462- 2911 -3

=4,

CIRCULATION OFFICE
Portland Place, Boulder, Colorado 80302

Member
Audit Bureau of
Circulations

Radio & TV News
Radio News
Radio -Electronic Engineering Trademarks Reg. U.S. Pat. Off.
SUBSCRIPTION SERVICE: All subscription correspondence should be addressed to Electronics World, Circulation Department. Portland Place, Boulder. Colorado 80302. Please allow at least six weeks for change of
address. Include your old address, as well as new -enclosing if possible an address label from a recent issue.
EDITORIAL CONTRIBUTIONS must be accompanied by return postage and will be handled with reasonable
care; however publisher assumes no responsibility for return or safety of art work, photographs, or

manuscripts.

ELECTRONICS WORLD (July, 1967, Vol. 78, No. 1 I. Published monthly at 307 North Michigan Avenue.
Chicago, Illinois 60601. by Ziff -Davis Publishing Company -also the publishers of Airline Management and
Marketing, Boating, Business & Commercial Aviation, Car and Driver, Cycle, Flying, HiFi /Stereo Review.
Modern Bride, Popular Aviation. Popular Electronics, Popular Photography. Skiing, Skiing Area News, and
Skiing Trade News. (Travel Weekly is published by Robinson Publications, Inc.. a subsidiary of Ziff -Davis
Publishing Company.) One year subscription rate for U.S., U.S. Possessions, and Canada, $6.00; all other
countries, $7.00. Second Class postage paid at Chicago, Illinois and at additional mailing offices. Authorized
as second class mail by the Post Office Department, Ottawa, Canada and for payment of postage in cash.

ELECTRONICS WORLD

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CIRCLE NO. 123 ON READER SERVICE CARD

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5

WORTH

LETTERS
FROM OUR
READERS

WAITING

SILICONIX FET'S

FOR!

To the Editors:
Your May issue contained an article
on "Field- Effect Transistor Circuits" by
Wujek and McGee. Most of these circuits use field -effect transistors produced
by Siliconix. However, in contacting the
company to get some of these FET's,
I have learned that the low prices
quoted at the very beginning of the
article are no longer in effect. As I recall, these prices were 81.00 for the
U -110 transistor or 82.75 for a package consisting of the U -110 and U -112.

act differently if we believe we are being observed,' Vice President Humphrey
has written. `If we can never be sure
whether or not we are being watched
and listened to, all our actions will be
altered and our very character will
change.' Associate justice William Brennan has limned another threat: 'Electronic surveillance, in fact, makes the
police omniscient; and police omniscience is one of the most effective tools
of tyranny.' "
PAUL BRADFORD

New York, N.Y.

ROBERT G. SIMPSON

D YNACO

Los Angeles, Calif.

Reader Simpson is quite correct in
that these low prices were the ones
quoted in a Siliconix ad that appeared

wrral

STEREO

120
3 years of intensive develop-

ment give you all the virtues of
transistorized amplifiers with
none of the harsh "transistor
sound."
The combined distortion of
the Stereo 120 and the PAS -3X

perfectionist's preamplifier
does not exceed 1 10 of 1%
from 20 to 20,000 cycles at
most useable power levels.
60 watts continuous power

per channel; fully regulated
power supply; complete electronic protection (no fuses or
thermal cutouts) against open
or short circuits; impeccable
specifications; modular design
for easy kit building.
Write for full specifications
and detailed test reports.

dynraco

3912 POWELTON AVENUE,
PHILADELPHIA, PA. 19104
CIRCLE NO. 121 ON READER SERVICE CARD
6

months ago in ELECTRONICS
ad represented ( limited
time offer and was intended to .stimulate use of the new FET's. The prices
quoted in the ad actually expired at
the end of February, and the company
reports that their mission has been accomplished in introducing FET's to a
large number of people.
For those readers who are interested
in using these transistors note, the
U -110, U-112, U -146, and U -147 are
available from local Siliconix distributors at prices of $5.25. $'4.55, $3.25,
and $2.95, respectively, in quantities
from 1 to 29. The manufacturer will be
glad to direct all inquiries for these
transistors to their local distributor.s or
will furnish the name of the nearest
distributor where such transistors may
be obtained. Write to Siliconix Inc.,
1140 West Evelyn. Avenue, Sunnyvale,
California 94086. -Editors
WORLD. The

ELECTRONIC EAVESDROPPING

To the Editors:
Apropos of your article on electronic
snooping, I thought a recent editorial in
Life magazine on the subject "Ways To
Control Snooping" expressed my sentiments exactly. One paragraph in this
editorial is as follows:
"But if lawmen have the power to
tap wires and bug rooms of people they
believe guilty, what is to prevent them
from overhearing the private words of
the innocent? Who has the right to
overhear, and for what purpose? 'We

To the Editors:
Your article on electronic eavesdropping ( April issue) vvas very enlightening. However, I have some questions.
(1) An Attorney General once said that
banging on the floor will disable a bug
for 15 minutes or so. Any truth to this?
(2) If I suspect that a room is bugged,
how can I hold a private conversation?
(3) Why do some bugs claim a hundred feet of range while others mention
thousands of feet? (4) How far away
can a bug detector find a bug? (5)
How effective are the tailing devices
mentioned in the article? (6) "The i\lan
From U.N.C. L.E." uses exotic communications systems. Are they for real?
joiiN NV. IIOLLANDER
Brooklyn, N.Y.

These are just a few of the questions
we have received on our eavesdropping
story. Very brief answers follow:
1. Only if you bang directly on or
near enough to the bug to damage it
will you stop operation. Otherwise nothing will happen except that you may
hurt your hand.
2. Whispered conversation can take
place if a radio, TV set, or music system is turned up to a reasonable volume. The louder background over-

shadows the conversation. The safest
place to avoid eavesdropping is in the
center of a large room away from furniture, walls, and overhead fixtures. Another ploy sometimes used is to converse in the bathroom with the shower
running.
3. Despite all claims, most r.f. bugs
commercially available can only reach
out 100 feet or so with any reliability.
(Continued on page 12)
ELECTRONICS

WORLD

MALLORY Tips

for technicians

IA-

Choosing electrolytic capacitors
for color TV
When you need to replace an electrolytic capacitor in a
color television, it pays to select the best. Your customer
has a lot of dough invested in his color set, and he
won't settle for less than top performance. And his eye
can see sub -standard performance in color that would
go unnoticed in black- and -white.
Color TV is tough on electrolytics. Ambient temperatures run hotter, because of the greater number of
tubes and resistors inside crowded cabinets. Ripple
currents are higher, so the capacitor has to do a better
job of getting rid of internally generated heat. Voltage
ratings are higher, too; most electrolytics in color TV
are 400 volts or higher.

It's no surprise that leading color TV makers are pretty
darn particular about the electrolytics that they use as
original equipment. They demand a true high -voltage,
not one
high- temperature, high ripple capacitor
that's simply made to sell at bottom price. And meeting
these demands is the way Mallory got to be the top
supplier of electrolytics for color TV. We're the guys
who pioneered the 85 °C capacitor, who have consistently increased ripple current capacity, and who have
the reputation of leadership in high voltage ratings.

...

Here's our tip of the month. To save yourself time, get a
copy of our new cross reference, "Exact Replacement
Metal Can Electrolytic Capacitors for Color TV ". It
lists the original part number and the catalog number
of the corresponding Mallory replacement for 38 leading
color TV manufacturers. To save yourself costly call
backs, use only the best ... and that's one of the
Mallory FP -WP series, made to original equipment
specs. To get everything you need for color TV service,
see your Mallory distributor. He stocks Mallory power
resistors, circuit breakers, carbon and wire -wound controls and Discap' ceramic capacitors.
For a copy of the Color TV cross reference, ask your
Mallory Distributor, or write to Mallory Distributor
Products Company, a division of P. R. Mallory & Co.
Inc., Indianapolis, Indiana 46206.

CIRCLE NO. 109 ON READER SERVICE CARD

July, 1967

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with makeshift

twist -prong capacitor replacements ?
When you substitute capacitor sizes and ratings,
you leave yourself wide open for criticism
you risk your reputation .. .
of your work
you stand to lose customers. It just doesn't
pay to use makeshifts when it's so easy to get the
exact replacement from your Sprague distributor!

...

(Continued from page 6)
Speech quality is passable in nand
cases, borderline in most, and unintelligible in a few.
4. Because of the very low power
Output and range of r.f. used, detector
pickups must be nearly in direct contact with the bug before they can detect
the presence of the bug.
.5. If you have ever listened to the
Citizens Band (especially in a large urban area), you will realize how difficult
it is to trail someone using a very low
power transmitter.
6. The requirements. of the story line
usually exceed electronic development.
At present, these exotic systems do not
exist. Neither do we know of any radiotelephones in shoes. -Editors
:r

LASERS FOR CARS

Get the right SIZE,

right RATING every time
with improved

SPRAGUE

TWIST -LOKS
CAPACITORS!

2,365 different capacitors to choose from!
The industry's most complete selection of twist -prong capacitors,
bar none. Greater reliability, too. Exclusive Sprague cover design

provides a leak -proof seal which permits capacitors to withstand

higher ripple currents.

To the Editors:
Your May issue had an excellent lead
article on "Automotive Electronics"
which described a short -range laser
ranging device for reducing the possibility of accidental rear -end collisions. As
I understand it, this device, being developed by General Electric, is a pulse echo- ranging system that uses infrared
light pulses in much the same way that
pulse radar is able to determine dis-

tance (range).
Readers may also be interested in
another approach involving a laser for
automobiles which is being developed
by Airborne Instruments Laboratory.
hI this system, a car would carry a
gallium -arsenide light- emitting diode
laser which would radiate infrared
pulses at about 200 Hz at all times.
These pulses would be confined by
means of inexpensive optics to a pencil
beam about 15° wide with a range of
perhaps 700 feet behind the car. Trailing automobiles would then pick up
the radiated laser energy and indicate
it in some simple way to the driver of
the following car.
It is planned to make the repetition
rate of the radiated pulses vary inversely with the radiating car's speed. For
example, when the car is moving slowly or standing still, the rep rate will
be high; as the car speeds up, the rep
rate will be reduced. If the detector
in the following car is made to respond
to these changes, it will be possible to
signal the radiating car's speed and
hopefully prevent a rear -end collision.
RIC:IIARD PARKIIURST

GET YOUR COPY of

San Francisco, Calif.

Sprague's com-

prehensive Electrolytic

Replacement Manual

Capacitor

K -108

from

your Sprague Distributor, or write
Sprague Products Co.,

Mar-

shall Street, North Adams, Mass.

SPRAGUE®
THE

WORLD'S LARGEST MANUFACTURER

MARK OF RELIABILITY

CAPACITORS

CIRCLE NO. 99 ON READER SERVICE CARD

Thanks to Reader Parkhurst for telling us about this interesting laser application. Dlany other companies, including the automobile manufacturers
themselves, are hard at work on prototype and experimental equipment to
improve the safety of their products.
Interestingly enough, ill reh of this
equipment is electronic. -Editors.
ELECTRONICS

WORLD

New Solid -State High Impedance V -O -M

The Unique New
Heathkit IM -25
Kit $80
Wired $115

The first of an exciting new line of Heathkit test instruments, the IM -25
Solid -State V -O -M does all the measurement jobs normally required in
tube or transistor circuits with the no- loading high impedance of a
VTVM, the convenience and versatility of a VOM, and the accuracy and
sensitivity of separate lab instruments.

Never Before Has An Instrument With These Features
and Performance Been Available At Less Than $200

Accuracy of the impressive specifications of the 1M -25 arc assured by
careful attention to design details. For example, the input of the IM -25
"floats," isolating the input circuit from the cabinet. (The cabinet is
grounded by a three -wire line cord.) Double Zener-diode regulation
minimizes zero shift when changing from line to battery operation.
Ohms scale calibration is a set -and- forget adjustment. DC voltage measurements require only a shorted input check of meter zero. Applied
voltage during resistance measurements is less than 100 millivolts from
a constant -current source to avoid the possibility of erroneous readings
or circuitry damage.

13 Silicon Transistors Plus 2 Field Effect Transistors. 11 Megohm
Input Impedance on DC 10 Megohm Input Impedance on AC 9 DC
Voltage Ranges From 150 Millivolts Full Scale to 1500 Volts Full Scale
Accuracy .3% Full Scale 9 AC Voltage Ranges From 150 Millivolts
Full Scale to 1500 Volts Full Scale ... Accuracy 5% Full Scale 7 Resistance Ranges, 10 Ohms Center Scale xl, x10, x100, x1 k, x10k, x100k,
Measures From One Ohm to 1000 Megohms 11 Current
xl Meg
Ranges From 15 Microamps Full Scale to 1.5 Amps Full Scale
Accuracy *4% DC, 5% AC AC Response to 100 kHz 6 ", 200 ua Meter
With Zero Center Scales For Positive and Negative Voltage Measurements Without Switching 1% Precision Resistors Separate Switch
For Each Function Eliminates Constant Changing
Ten -Turn Thumb wheel Zero Adjustment For Precision Settings Built -In 120 /240 VAC,
50 -60 Hz Power Supply Plus In- Cabinet Holders For Battery Supply
During Portable Operation Easy Circuit Board Assembly New Heath
Instrument Styling With "Unitized "" Construction and Low Profile
Appearance Color Styled in Handsome Beige and Black
.

Those who choose the kit model IM -25 rather than the factory assembled
and tested version will find it far easier to build than any other kit meter
we've ever offered. All components mount on just one circuit hoard
even the switches. No more tedious divider circuit wiring. And a special
wiring harness is provided.

...

A die-cast panel bezel ties both front and rear panels together- with the
circuit board supported between to permit removal of the cabinet shells
without impairing operation. Convenient carrying to indIes are recessed
in each of the cabinet shell mounting strips.

IM -25 SPECIFICATIONS
DC SECTION: Voltmeter: Ranges: 0
0 -15, 0.5, 1.5, 15, 50,
150, 500, 1500 volts full scale. Input Resistance: 11 megch,r,s on oll ronges. Accuracy: t3'
-

of full scale. Milliammeter: Ranges: 0 - .015, 05, 0.15, 0.5,
5, 5, 15, 50, 150, 500, 1500 mu
full scale. Input Resistance: 0.1 ohm (1500 roo) to 10 K ohm (0 015 ma). Accuracy: oof
full scale. AC SECTION: Voltmeter: Ranges: 0 0.15, 0.5, 1.5, 15, 50, 150, 500, 1500 volts
full scale. Input Resistance: 10 megohm shunted by 150 uaf. (Measured at probe tip.! Accuracy: '°S
of full scale. Frequency Response: 32 db 10 Hz - 100 kHz. Milliammeter:
Ranges: 0 - 0.015, 0.05, 0.15, 0.5, 1.5, 5, 15, 50, 150, 500, 1500 ma. full stole. Input Resistant once: 0.1 ohm (1500 ma) to 10 k ohm (0.015 ma). Accuracy: g, 5'; of full scale. Ohm Meter:
Ranges: 10 ohm center scale xl, x10, x100, xl k, x10k, x100k, xl meq. Probe: Combined AC OHMS - DC switching probe, single jack input for Probe and Ground connections, Circuit
ground isolated from cabinet. Dividers: I `; Precision Type. Meter: 6 ", 200 ua, 100 movement.
Transistors, Diodes: 2 - 2N4304 FETronsistor; 13 - 2N3393 silicon junction transistor;
9.1 V zener diode; -13 V zener diode; 4-1N191 germanium diode;
silicon Power Supply diode.
POWER SUPPLIES: Ohms Circuit: 3 volts, (C - cells). Ohms Circuit Bias: 1.35 volt (ElN
Mercury Cell). Amplifier Circuit: 18 volts. Battery Operation: C cells. Line Operation:
Transformer operated ix wove circuit, operable on either 120 or 240 V AC 5060 Hz.
1

Whether you choose the factory assembled model or the kit version, we
believe you will lind the 1M -25 a significant step forward in design and
value
capable of creditable service in any application.

...

Kit IM -25, 10 lbs.
Assembled IMW -25,

*Ma

MM WM

Man

10 lbs

$80.00
$115.00

MW MO MW MM MM WM WM WM

HEATH COMPANY, Dept. I5.1

FREE
CATALOG

Benton Harbor, Michigan 49022
L] Enclosed is

plus shipping.

Please send model (s)

Describes these and over 250 kits
for stereo.' hi -fi, color TV, amateur
radio, shortwave, test, CB, marine,
educational, home and hobby. Save
up to 50% by doing the easy assembly yourself. Mail coupon or write
Heath Company, Benton Harbor,
Michigan 49022

Please send

FREE

Heathkit Catalog.

Name
Please Print)
1

Address
City
Prices

State
specifications subject to change without notice.

ZipTE -158
>

July, 1967

CIRCLE NO.

14 ON READER SERVICE CARD
13

www.americanradiohistory.com

HI -FI PRODUCT

ßEPURT
EW

TESTED BY HIRSCH -HOUCK LABS

Bogen TR -100X Stereo Receiver
Wharfedale W20 Speaker System

LAB TESTED

Bogen TR -100X Stereo Receiver
For copy of manufacturer's brochure, circle No. 34 on Reader Service Card.

f:1

144

!1IN

and highs as the setting is reduced.
There is no provision for disabling the
loudness compensation. A separate balance control adjusts channel balance.
The driver transistors are transformer- coupled to the output transistors
which, in turn, are direct -coupled to
the speakers, without blocking capacitors. A fixed -response roll -off below 20
Hz prevents damage to transistors or
speakers by subsonic transients. A
front -panel switch selects either or both
of two pairs of speakers or switches the
outputs to a front -panel headphone
jack. The control complement is completed by two slide switches for a.c.
power and stereo mono selection (effective on all inputs)
The FM tuner of the TR -100X is
rated at 2.7 microvolts IHF usable sensitivity. We measured it as 2.9 eV, well
within the limits of normal measurement tolerances. The TR -100X was
non -critical to tune and had a little over
1l distortion at 100% modulation.
The FM frequency response was ±1.5
.

THE Bogen TR -100X solid -state AM-

modulator has traps which very effectively eliminate SCA interference
(whistles and birdies) from the background of FM- stereo broadcasts. The
38 -kHz oscillator is gated on automatically by the 19 -kHz pilot carrier, which
also synchronizes it. A separate transistor operates the incandescent stereo indicator lamp on the dial face.
The audio section has a pair of two stage feedback -type phono equalizing
preamps and switched inputs for AM,
FM, Phono, and Aux. The Tape -Output
jacks supply the selected signal to a
tape recorder, unaffected by volume or
tone controls. There is no provision for
monitoring from the tape. The tone
controls act on both channels simultaneously. The volume control is loudness- compensated, boosting both lows

FM stereo receiver combines operating simplicity with ample control
flexibility for most users, and at a
moderate price, Using silicon transistors throughout, the TR -100X has a
sensitive, stable FM tuner, an AM
tuner, dual preamplifiers, and a pair of
30 -watt (music power) amplifiers.
The FAI tuner has a tuned r.f. amplifier, three i.f. stages, and a ratio detector. The shielded front -end also contains the AM oscillator and the tuning
capacitor for the AM r.f. amplifier. Two
of the FM i.f. stages do double duty as
AM i.f. amplifiers. The tuning meter
(which is tuned for maximum reading)
operates from the AM detector or from
a diode detector in the FM i.f. section.
The switc ii 1g-type multiplex deIo.O

10.0

BOGEN TR -100X

BOTH CHANNELS DRIVEN
B11 LOADS, 1205.2.C. LINE
(ONE CHANNEL MEASURED)
REF. -POWER OUTPUT (20W)
HALF -POWER OUTPUT( -3dB)

5.0

-- -LOW

POWER OUTPUT

dB from 30 to 15,000 Hz. Stereo channel separation was better than 30 dB
from 150 to 1000 Hz and better than
20 dB from 30 to 10,000 Hz.

The amplifier

frequency response

±1

dB from 20 to 20,000 Hz at
maximum volume setting. At normal lis-

was

tening levels the loudness compensation boosted lows by about 10 dB and
highs by about 5 dB. The bass tone
control affected on y frequencies below
100 Hz at fist, pre gressively exte idi) g

BOGEN TR -IOOX
BOTH CHANNELS DRIVEN

-1
- - --60

BR LOADS, 120V.A.C.L NE

5.0

(-100)

(ONE CHANNEL MEASURED)
Hz TOTAL HARM DST.
/7000 Hz 14:I IM DIST.

2.0

Z 2.0

á
v, I.0

/
--

0.5

0.2

O.I

100

200

500

FREQUENCY

1.0

-H

10k

20k

0.1

CONTINUOUS(EOUIV.) SINE -WAVE POWER OUTPUT PER

20
50
CHANNEL -WATTS

CIRCLE NO. 198 ON READER SERVICE CARD

www.americanradiohistory.com

100

5881
Your Sylvania distributor can

analyze your electronic replacement
needs. To save you time and money.
GONMUNICIAYIN>wl

jVALin

He can do an inventory analysis for you -at no cost.
You'll learn which tubes to stock in quantity -and
which ores not to. You'll prevent emergencies when
tubes and semiconductors need replacing.
Your Sylvania man is a tube ar_c semiconductor expert. Because he's always in tcuch with Sylvania

5881

6680/1 2AU7A
L_

product ar d applications engineering staffs, so he's
always kept up to date.
And we furnish him with detailed technical ir.formation about tube and semiconductor applications
-industry by industry. So he knows your prob =ems
-and has the answers.
Help yoc.raelf to a free analysis of your replacement need3. Gall your nearby Sylvania distribitor
now. YoTl= save yourself some trouble. And money,
too.

Sylvania Electronic Tube Division, Electronic Components Group, Seneca Falls, New York 13148.

46B/ 8298a

SI'LVANIA
l
GTE
V
SUBSIDIARY O

GENERPL-ELEPHONE & ELECTRONICS

2021

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GB1?52$ USA

----

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5551

If it moves,

[

-5

The Antenna Specialists

iiii1

have a great new CB antenna
to help

it communicate!

I
-ii®iii
-i

,REQUENCY RESPONSE
e

;

BOGEN TR 00X
RCVR. (STEREO)

Id
CC

-25

I;:

SEAR ATION

30
-35

-40

200

500

20k

10k

FREQUENCY -Hz

to about 300 Hz as it was rotated to its
limits. This is an excellent characteristic, well suited to removing the effects
of the loudness compensation if this is
New "Grip- Stick" magnetic mount sticks
to its business at all legal speeds! VSWR
less than 1.5/ 1.0, capacity- matched. 16'
cable. Less than 27" long. No -mar vinyl
underside Model M -168.

ew "Sea- Hook" Half- wave
marine
ntenna has exceptionally low radiation
ngle. No ground plate required! Spring loaded fold -down feature. White cycolac
ase, chrome -plated brass parts. VSWR less
an 1.5'1.0. Model ASM -23.

Ìew "Sky-Hook" fiberglas

CB an-

tenna- low -profile design, wind -rated over
250 mph. Temp. range: minus 50 °Fl plus
200 °F. VSWR 1.5/1.0 or better. Only 24"

ng- reduces static,
1

gives ample ground

M-149.

the antenna
specialists co.
Div. of Anzac Industries, Inc.
12435 Euclid Ave., Cleveland, Ohio 44106

Whatever your need, you can

trust the "Stripes of Quality "!
Export: 64 -14 Woodside Ave,
Woodside, N.Y., 11377

CIRCLE NO. 124 ON READER SERVICE CARD
16

desired. The RIAA phono equalization
was flat within ±1 dB from 150 to
15,000 Hz, rising to -{-4 dB in the
vicinity of 40 IIz.
We pleasured a maximum power
output of 20 watts per channel into
8 -ohm loads, with both channels driven.
Into 4 ohms, the power was reduced
about 50% and into 16 ohms it was increased about 20 %. The manufacturer
does not supply continuous power ratings, so it is not possible to correlate
these figures with his 30 -watt music power rating.
At 20 watts, the harmonic distortion
was about 1% from 200 to 2000 Hz,
rising to 2% at 50 and 15,000 IIz. At
half power, distortion was under 1'
from 20 to 20,000 Hz, and less than
0.4% over most of this range. At 2
watts output (a normal maximum listening level) the distortion was between 0.2% and 0.3% over most of the
audio range, reaching a maximum of
about 0.7% at 50 Hz.
The 1000 -Hz harmonic distortion
was under 0.15% at power levels below 1 watt, rising to 0.3 at 5 watts
and to 1% at about 17 watts. Heating
of the output transistors during the
high -power measurements affected the
distortion somewhat snaking a direct
comparison between the two distortion
curves difficult. The IM distortion rose
smoothly from 0.5% at low levels to

111Ai

ÍII

AUDIO OUTPUT
US=O.7BV (TAPE OUTPUT)

SRCER.(MONOO1x

-20

III

i
á

-30

11-IF

USABLE SENSITIVITY 2.9}JV

-40
TOTAL NOISE, HUM, DISTORTION
---MOD.
AT 4001-Ix
!

:HI
SO

100

INPUT -MICROVOLTS

RE:100 /

200

SO,

100

2% at 8 watts and to a value of 3% at
15 watts.

The TR -100X audio amplifiers could
be driven to 10 watts output by as little
as 2 millivolts on phono inputs or 0.14
volt on Aux. inputs. Hum was inaudible, about 76 dB below 10 watts on
Aux. and 57 dB below 10 watts on
Phono ( the latter being almost entirely

hiss).
We found the unit to be a very satisfactory FMI- stereo receiver which tuned
easily and has excellent sensitivity and
audio quality. The loudness compensation produced excessively bassy sound
with relatively efficient speakers which
required low volume- control settings.
However, the bass tone control was able
to restore a satisfactory balance.
The Bogen TR -100X sells for $249.95.
Walnut -finished cabinets are available
in metal for $14.95 and in wood for
$24.95.
A

Wharfedale W20 Speaker System
For copy of manufacturer's brochure, circle No. 35 on Reader Service Card.
ANEW addition to the growing list of cloth grille is removable, being held in
what might be termed "miniature" place by hook -and -pile fastener strips.
loudspeaker systems is the Wharfedale The speaker impedance is rated at 4 to
W20. Measuring only 14" x 9 %" x 8)2' 8 ohms.
deep, this diminutive box delivers a very
We averaged data taken at eight locarespectable amount of good -quality tions in our room to derive a composite
sound.
frequency response curve. A rather
The W20 is a two -way system, with prominent peak occurred at about 100
an 8" high -compliance woofer and a 3" Hz, followed by a slight depression at
dome- radiator tweeter. The tweeter lev- around 200 Hz. (This was partly the reel is adjustable by means of a continuous
sult of room resonances (chick we have
control on the rear of the enclosure. The observed around 100 11z with previous
ELECTRONICS WORLD

350 W. @ 25°

290 W. @ 25° C

RELATIVE VOLTS- AMPS /$1.00 COST

olitron, now it full production of the SDT 8950/
SDT 8650 families, has reduced the price of these fast
switching, high power silicon transistors. As shown on
the comparison Volt -Amp chart, these transistors provide more power -handling capabilities per dollar than

50
40

2N3080
30

multiples of similar, limited- source devices. In order
to meet various size and weight requirements, they are
available in either 1 1/16" hex or TO -68 packages. A
few of their many uses include visual display circuits,
converters, inverters, voltage regulators and /or space
flight applications.

VCEO

2N2583

10 --

PERFORMANCE SPECIFICATIONS

DESIGN LIMITS
VIBR)CBO

2N3585

VIBRIEBO

VBE (Sat)

h FE

VcE(sat)

ICBO

(SUS)

Type

Volts

Number

Volts

TO -68

HEX -CASE

Ic =1mA
Min.

Min.

Max.

SDT8651

SDT8951

200

SDT8652

SOT8952

225

SDT8653

SDT8953

250

SDT8654

SDT8954

275

SDT8655

SDT8955

300

=0.2A

CONTACT

=1mA

=40A,

VcE

=10V

=40A,

Volts
IB

=6A

VcE

=100V

Max.

Typ.

2.0

TODAY FOR COMPLETE INFORMATION

olitron

DEVICES, INC.

1177 BLUE HERON BLVD. / RIVIERA BEACH, FLORIDA / (305) 848 -4311

/ TWX:

(510) 952 -6676

Leader in Germanium and Silicon Transistors, Cryogenic Thermometers, High Voltage Rectifiers, Hot Carrier Diodes, Temperature Compensated Zeners,
Voltage Variable Capacitors, Random/ White Noise Components, Microelectronic Circuits, and Power -Sink Interconnection Systems.
CIRCLE NO. 199 ON READER SERVICE CARD
17
July, 1967

www.americanradiohistory.com

v/ .,f.7""/

Enjoy the "music- only" programs
now available on the FM broadcast
band from coast to coast.

NO COMMERCIALS
NO INTERRUPTIONS

speaker response curves.- Editor) Above

that frequency the response was very
smooth and fiat, rising slightly to +6 dB
at 12,000 Hz. This was measured Nvith
maximum treble level, and can be adjusted downward as desired by the
listener.
The harmonic distortion at a 1 -watt
drive level was very low down to about
70 Iiz, rising smoothly to 10% at 55 Hz.
We would judge the effective lower lirnit of the \2O's frequency response to be
about 50 Hz, which is very respectable
for a speaker encompassing only about
cubic foot. The tone -burst response
was good throughout, with no sustained
ringing or spurious output frequencies,
as shown below.
The efficiency of the speaker system
is moderate, which means that it can be
driven by an amplifier of 20 or more
watts, rated output. We would not saggest its use with the very low- power,
budget- priced amplifiers which can only
deliver b to 10 watts, since the speaker
thrives on surprisingly large amounts of
drive power. As an example, we used it
with a 40 -watt transistor amplifier, and
it withstood the full output of the amplifier without any signs of breakup or
excessive distortion -and, at the sane
time, the loudspeaker delivered an astonishing volume level.
There is an illusion of more bass than
the \V'20 actually puts out, which is
probably due to the emphasis in the
I00-Hz region. It does not sound tubby
or unnatual, however. The speaker has
A

Its easy! Just plug Music Associated's Sub
Carrier Detector into multiplex jack of your FM
tuner or easily wire into discriminator. Tune
through your FM dial and hear programs of con tmuous, commercial -free music you are now
missing. The Detector, self- powered and with
electronic mute for quieting between selections,
permits reception of popular background music
programs no longer sent by wire but transmitted
as hidden programs on the FM broadcast band
from coast to coast. Use with any FM tuner.
Size 51/2" x 9 ". Shipping weight approx. 7 lbs.

KIT

$4950
$7500

with pre -tuned coils, no alignment necessary)

WIRED
COVER

$4.95 EXTRA

current List of FM Broadcast Stations with SCA
.authorisation
55.00

MUSIC ASSOCIATED
65 Glenwood Road, Upper Montclair, New Jersr.

Phone: 1201)-744 -3387

CIRCLE NO

106 ON LEADER SERVICE CARD

WORLD'S
FINEST

a very pleasing easy sound, with excellent definition in complex orchestral pas-

sages. We found it preferable to operate
it with the treble level control turned
down considerably for over -all balance,
but this can be expected to vary with
the characteristics of the individual listening room.
A speaker of this size and price must
not be judged by the same critical standards as far larger and more costly systems. For use in limited space applications, it should acquit itself admirably.
It sounds good and is thoroughly listen able even if it will not convince the
listener that he is in the concert hall. We
feel that its low distortion is a strongly
contributing factor to its " listemtbility"
and it is unlikely to wilt under the full
drive of most powerful integrated receivers.
The price of the Wharfedale ÁV20 is
S49.95.

.!.

TONE BURST

TONE BURST
1

WHARFEDALE W20 SPEAKER SYSTEM - FREQUENCY RESPONSE
CORRECTED FOR ROOM RESPONSE BELOW I000HxAVERAGE OF e INDOOR RUNS

1_r1

-1,,

100

200

500

AIIt

I11

20k

IOk

tW;
mop`r

I-WATT INPUT

71T-111101r
i

l',

if---

FREQUENCY-Hz

ERSIN

MULTILORE

ONLY

69C

BUY IT AT RADIO-TV PARTS STORES
MULTICORE SALES CORP., WESTBURY, N.Y. 11590

LASER MEASURES OCEAN WINDS AND WAVES
Arecent demonstration by Electro -Optical Systems, Inc,, has shown that
a c.w. laser operating within an aircraft
(lying at high altitudes could be directed
to an ocean area directly beneath the air-

craft and, by recording the reflected intensity of the beam tux a function of the
viewing angle, a three -dimensional intensity pattern could be constructed to show
prevailing wind fields existing at the surface. By further imposing a microwave
frequency on the optical carrier, a reflective phase displacement signal can be

CIRCLE NO. 107 ON READER SERVICE CARD
18

detected which is directly translatable
into wave amplitude. The readout then
becomes, in effect, three dimensional.
It was 110i led Out that if used aboard
observation -type aircraft, the surface
evaluation system could detect build-up
of heavy. .seas and winds almost instantaneously in those areas of the .atlantic
and Pacific not normally covered by
existing meteorological networks and
could thus give valuable aid to the tactical
deployment of both surface and subsurface vehicles.
A

CIRCLE NO. 200 ON READER SERVICE

www.americanradiohistory.com

CARD

(La,
,

f Powo

ha.,,

Advanced fabrication techniques result in higher quality at lower cost
Two Compact Models Now Available... 0 -25 Volts

0 -400 MA... 0 -50 Volts

0 -200 MA

0.01% Regulation

VOLTAGE
COARSE

IhPIHARRISON
HE W LETT PACKARí1-

6217A POWER SUPPLY
0 -50 VOLTS

200mA

FIRST CLASS

PERMIT NO. 20
BERKELEY HEIGHTS, N.J.

BUSINESS REPLY MAIL
No Postage Stamp Necessary If Mailed in the United States
w

Pos:age Will be Paid by Addressee

HEWLETT PACKARD

/ HARRISON DIVISION

100 Locust Ave., Berkeley Heights

New Jersey 07922

Attn: Sales Manager

VOLTAGE

FINE

METER

HARRISON

SELECTION

VOLTS

PA HEWLETTPACKARD

4 mA

621 7A POWER SUPPLY

0- 50

VOLTS 200 mA

Actual Size

The NEWEST CONCEPT in Bench DC Power Supplies
Two extremely compact, well -regulated DC power supplies designed
especially for bench use have just been added to the hp power supply
line. New fabrication techniques have been employed for these supplies
to minimize manufacturing costs while retaining component and circuit
quality. Reliable, yet low cost, these "hand- size" battery substitutes have
over -all performance features ideal for circuit development, component
evaluation, and other laboratory applications.
The all- silicon circuit uses an input differential amplifier to compare the
output voltage with a reference voltage derived from a temperature compensated zener diode. These stable input and reference circuits are
combined with a high gain feedback amplifier to achieve low noise,
drift -free performance. Output voltage is fully adjustable down to zero.
Special design precautions prevent output overshoot during turn -on or
turn -off, or when AC power is suddenly removed.
The front panel meter can be switched to monitor output voltage or
current. Constant Voltage/Current Limiting insures short -circuit -proof
operation, and permits series and parallel connection of two or more
supplies when greater voltage or current is desired.
The molded, impact- resistant case includes an interlocking feature for
stacking several units vertically, thus minimizing bench space required
for multiple supplies. Alternatively, up to three units can be mounted side
by side on a standard 31/2" H x 19"W rack panel.

Gentlemen
I

Output:

Model 6215A
0 -25V at 0 -400 MA

Model 6217A
at 0 -200 MA

0 -50V

Either positive or negative output terminal may be grounded, or the
supply may be operated "floating" up to 300V off ground.
AC Input:

105-125 VAC*, 50-400 Hz

Load Regulation:

0.01%+

Line Regulation:

0.01%

Ripple & Noise:

<200 µv
<0.02%

Temperature Coefficient:

Stability for Eight Hours
After 30 Minutes Warm -up:

4 MV
RMS

MV/°

<0.1% + 5 MV
<50 As for output recovery to

Transient Recovery Time:

within 10 MV following a full
load change
Output Impedance:
<0.03 ohms from DC to KHz
<.5 ohms from KHz to 100 KHz
<3 ohms from 100 KHz to MHz
Maximum Ambient Operating Temperature: + 55 °C
1

31/4" (8.26 cm) H x 51/4"
(13.34 cm) W x 7" (17.78 cm)
51/4 lbs (2,38 kilograms)
$90.00
$90.00

Size:

Weight:
Price -Model 6215A:

Model 6217A:

'210 -250

VAC input also available

am interested in the Bench Series Model 6215A and 6217A for the

following application
Please send additional data
Please send ordering information

HEWLETT
PACKARD 11E HARRISON

Have an hp sales engineer call for an appointment

(phone number below)

MI DIVISION

Please send your '67 Catalog and Power Supply Handbook

Name
100 Locust Ave., Berkeley Heights, New Jersey 07922

Title

Telephone 201- 464-1234 TWX 710 - 984 -7972

Company
Address
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Printed in U.S.A.

Interior of spin balance facility at Cape Kennedy, following the accidental ignition of an X -248 rocket motor on April 14,
1964. The Orbiting Solar Observatory B spacecraft was mounted on top of the motor and alignment tests just completed
when the accidental ignition occurred. The spacecraft was badly damaged and 11 persons working in the building were injured -two fatally. The X-248 rocket was the third stage on a Delta launch vehicle which had been scheduled to orbit OSO B.

STATIC ELECTRICITY:
The Space Age's Billion -Year -Old Gremlin
By EDWARD A

LACY

Discharges from static electricity have accidentally fired
missiles, damaged semiconductors, and produced aircraft
explosions. here is hots danger is detected und minimized.
BACK before the Gemini experiments, space engineers
believed that a spacecraft could acquire a substantial
charge of static electricity from rubbing against the
atmosphere on the way to space and from engine operation
while in space. Such a charge could destroy sensitive semiconductor circuits, they reasoned, or cause a circuit to turn
on at the wrong time. As bad as this may seem, it was nothing compared to another nagging worry of the designers.
Imagine, they said, an astronaut walking in space approaching another spacecraft or perhaps his own ship. Just
as he starts to touch it, a fat spark of static electricity jumps
from his hand to the craft, burning a hole in the thin skin
of the spacecraft and possibly causing the fuel on board to
explode.
Just to make sure it didn't happen, the engineers installed three copper fingers on the Agena target docking
adapter so that any potential difference between it and the
Gemini could be slowly bled off through a resistor bank.
Naturally, the engineers were greatly relieved when the
static discharge monitor on the Agena told them that static electricity simply is not a problem in space.
But while static electricity may not be a problem in

space, this bil lion -year -old gremlin nonetheless presents
difficulties for the space age and particularly for the missile industry. At Cape Kennedy, for example, no one wants
to be working around live missiles when lightning -a form
of static electricity -is nearby. Unfortunately for the safety
engineers, lightning is often close by at the Cape, since
Florida has more thunderstorms than any other area in the
country. Not only are these thunderstorms frequent but
they are also powerful]. In 1965, one of the launch gantries
was struck by a stroke which registered 151,000 amperes.
As dangerous as these strokes may be, it is significant to
note that only a slight discharge of static electricity can
cause disaster, as the missile engineers have learned from
tragic experience. For instance, early one spring morning
in 1964 at the Cape, technicians and mechanics in the
spin -test facility were preparing to move the third stage of
a NASA Delta rocket. Someone had just removed a protective plastic sheet from the motor when the motor suddenly
ignited, lifted off, and flew to the end of the 100 -footlong building. In the process five men were burned critically (two later died) by the 3000° exhaust from the motor.
The suspected cause of the whole affair: static electricity

July, 1967

www.americanradiohistory.com

from the protective plastic cover used.
is still present with the new insulated Fortunately, when we encounter statgate field- effect transistors. The gate
ic electricity the results are not so traginsulation on these devices can be deic. On dry winter days we may get a
stroyed by the static electricity genertingle or perhaps a jolt if we shuffle
ated by (1) the transistor sliding around
across a carpeted floor and then touch
in its plastic shipping container or (2)
a metal desk or doorknob. Self- protecby the electrostatic body potential of
tion is simple: slap the metal object
the technician who is wiring the unit
with the palm of your hand before atinto a circuit.
tempting to use it, or touch the doorOne semiconductor manufacturer is
knob with a tightly held key before
planning to place a zener diode across
opening the door.
the gates in its FET's in the near future
However, while static electricity may
to alleviate this problem. Until this is
sometimes be a source of shocking discommon practice, however, technicians
comfort, it may also be a source of joy
are advised to discharge their bodies
and comfort, according to recent studand to ground the tips of their solderies. At the Stanford Research Institute,
ing irons when working with FET's.
scientists recently used a sensitive statIn most cases, static electricity is
ic detector called a "feed mill" to meagenerated by friction. When the plastic
sure the electrostatic processes associface of a test instrument is polished,
Chimney shows severe damage which
ated with the breakup of water droplets
was caused by a lightning stroke.
for example, enough electricity may be
ill a bathroom shower. The results of
created to attract the needle of the
their study show that the exhilarating effect of a shower may
meter to the face and result in an inaccurate reading.
be due to negative electricity instead of the warmth and
However, static electricity can be produced by electroforce of the water.
static induction and by contact and separation of materials.
Electronics enthusiasts have long been familiar with the
In the latter case, electrons may move from one material
problems of static electricity in phonograph records, tranto another as when belts pass over pulleys or when automosistors, instrument meters, and automobile tires.
bile tires run on highways. If the materials are then sepaIt is no secret, for example, that the plastic used in phorated, one object will have a surplus of electrons (negativenograph records can be given high static, electricity charges
ly charged) and the other will have a deficiency of electrons
which, unfortunately, attract dirt, dust, and fluff to the
(positively charged). A surface is considered to be very
grooves. Naturally, such particles cause noise and distortion
strongly charged if it has a deficiency or excess of only one
as well as damage to the record. The problem has become
electron in 100,000 atoms.
even more acute with stereo records and with modern pickShock Hazard and Explosion
ups which track so lightly that they ride over the dust particles instead of pushing them aside.
A static charge may have a potential from a few volts to
What are the record manufacturers doing about the probseveral hundred thousand volts. Since the human body
lem? One company has added the anti -static agent Catanac
can develop up to 10,000 volts under certain conditions, it
SN to its high -quality records to stop the problem at its
is not uncommon to find charges measuring from 5000 to
source. It is interesting to note that another major manu10,000 volts.
facturer says such agents are costly and that still another
A static voltage as low as 1500 volts can be felt if the
manufacturer claims that the use of sufficient additives to
little finger is slowly and carefully brought to within a few
eliminate static electricity causes the sound quality of the
thousandths of all inch of a charged body, says the Bureau
records to suffer.
of Mines. Why, then, don't such high voltages cause seriAdditional electronics problems with static electricity
ous injury or death? Simply because the current is so small.
involve transistors. Some years ago it was noticed that
The Bureau explains it as follows: "A current of 1/z ampere
when transistors were inserted into Styrofoam blocks for
( that is, '/r coulomb of electricity per second) is needed to
temporary storage, the very act of pushing the leads into
light an ordinary 4.5 -volt flashlight to full incandescence.
the Styrofoam sometimes generated a static charge great
It would require 500,000 people, charged to 5000 volts
enough to destroy the device.
each, to hold a total quantity of 2 coulomb of electricity."
Although this problem has generally been overcome, it
The static electricity on one's body may be enough, however, to ignite highly flammable dusts, gases, and vapors.
In fact, a charge that can barely be felt, seen, or heard has
Electrostatic discharger mounted on side of fuselage of helicopter.
more than enough energy to ignite flammable mixtures.
Annual fire and explosion losses from static electricity
have been estimated as high as $100,000,000. This figure
takes into account such diverse explosions as those in hospital operating rooms, munitions factories, and airliners.
For example, an inquiry board concluded that the 1959
crash of a TWA plane in Italy was caused by a gasoline explosion touched off in flight by static electricity.

Lightning
Lightning causes many explosions and fires. As a tremendously powerful static electricity spark, a single bolt
may have a potential of 100 million volts and produce a
current of 200,000 amperes. Such bolts are classified as
either "hot" or "cold." A hot strike lasts up to a tenth of
a second and sets fire to flammable materials in its path,
while a cold strike is faster and has an explosive rather than
an inflammatory effect.
The lightning- protection industry has gone undercover
22

ELECTRONICS

www.americanradiohistory.com

WORLD

tvitla rtoich of its equipment.
ent. five -fooltall lightning rods with ornamental
colored glass balls have given way to
10- inch -tall `air terminals" which may
be the only parts that show in a modern system. The conducting cables to
ground are hidden from sight either in
the framing or behind ridge rolls or

necting a wire from the objects to
ground, they become bonded and
grounded.
Since static electricity currents are
measured in microamperes, a very low
resistance ground, as normally required
in electrical work, is not needed. In
fact, in hospital operating rooms, where
anesthetic guises can be ignited by a
spark, low- resistance grounds are deliberately avoided. The floors in these
rooms arc made just conductive enough
to drain off static charges but not conductive enough to be a standard elec-

downspouts.

Does a grounded "f \' antenna pro vide lightning protection'? No, says the
Lightning Protection Institute, \wheel'
is sponsored by the lightning -protection
industry. The Institute says that the
average antennas does not have a long
trical hazard.
enough ground wire and does not have
Humidification. During the winter
enough paths to ground. Ordinary anmonths when the relative humidity
tenna grounding, the Institute states,
goes down, static electricity becomes
protects against accidental energization
obvious, especially when one walks
Van de Graaff generator shown here
from electrical service but it cannot be
across a carpet and touches a metal
with the pressure vessel removed.
expected to ground lightning, which
doorknob. On the other hand, during
has an amperage that may be more
the summer when the humidity is high,
than one thousand tunes greater than ordinary house current.
static electricity may scarcely be noticed.
When the humidity is high, some materials may absorb
Static Detectors
moisture, become more conductive, and thereby allow static
To effectively eliminate of control static electricity, it
charges to leak off. Such a condition, it should be noted,
has nothing to do with the conductivity of air since water
is necessary to use sensitive instruments to detect and oteasture it. Such instruments include the gold -leaf electroscope,
vapor does not make air electrically conductive.
At one time it was thought that this high humidity could
peon lamps, electrostatic voltmeters, and vacuum -tube
be used to reduce the hazards and nuisance of static elecelectrometers. All these devices are characterized by very
tricity. Thus, in some factories and hospital operating rooms,
high input impedance.
the humidity was raised to 70%. Not only was this hard
The simplest of these and the one so often seen in eleon the workers and expensive machinery, but it didn't
mentary science demonstrations is the gold -leaf electrowork often enough to make it worth the expense and disscope. In this device, the gold leaf is attached to a metal
comfort.
rod. AWhat the rod is brought near a charged body, the leaf
Static Eliminators. Radioactive static eliminators use
is repelled from the rod (or itself) because like charges
radium or polonium to ionize the air. While such devices
repel. \\'ith the electroscope, charges as low as 350 volts
offer safety from explosions, they are naturally a hazard
can be detected.
to anyone working nearby and therefore must be carefully
A neon lamp or fluorescent tube can be used in some apshielded when installed.
plications to indicate the presence of static electricity since
High -voltage eliminators apply a high voltage ( 3000 to
it tvill light feebly near voltages of 100 volts or more if
15,000 volts) to a series of points close to a grounded surone terminal is grounded or held in the haul. Even a
face. The voltage across this gap will discharge most
burned -out fluorescent tube can be used.
charged items that are placed in the gap.
Electrostatic voltmeters are employed to measure very
Static combs are grounded metal bars with needles or
high voltages such as those encountered mound radar, oswire brushes. When a charged body ( such as a flow of
cilloscopes, and Van de Ç ;rauff generators. These voltmeters
paper) goes by such a comb, the charged body ionizes the
derive their torque from the attraction of charged metalgap between it and the comb, thereby discharging itself.
lic surfaces; the stationary surface or vane is highly insuAir guns combine an air stream with an anti- static spray
lated with materials such as polystyrene. With insulation
in tt Band- :Meld air gun which is useful for cleaning plastic
resistance as ]sigh as 3 X 10' ohms, the leakage current
pats.
(Continued on page 67)
of these voltmeters is so low that sometimes they must be
shunted by a resistance in order to measure varying static
Lightning rods have been replaced by inconspicuous "air terminals ",
voltages.
whose ground resistance is shown being checked in the photograph.
The vacuum-tube electrometer is a simple vacuttnt -tithe
circuit with a ureter in the plate circuit to indicate current
flow. An antenna or probe is connected to the grid of the
tobe; when the probe is brought near a charged body, the
plate current will increase if the body is positively charged,
or the plate current will decrease if the body is negatively
charged.

Control of Static Electricity
Once a static electricity problem has been detected and
measured, it can be controlled or eliminated by (1) ground ing and bonding, (2) humidification, (3) static eliminators, and (4) anti-static. sprays.

Grounds and

1300d.s.

When two (or more) conducting

bodies are connected together with a conducting wire, there
will be no potential difference between them and static
sparking will not occur. In this condition, the objects are
said to be bonded. Although bonded, these objects may still
have a potential compared with ground. By simply conJuly, 1967

www.americanradiohistory.com

RECENT

DEVELOPMENTS

IN ELECTRONICS
Fuel Cells Under the Hood. (Top left) An electrically driven
army truck which derives its power from fuel cells, was demonstrated recently. Four fuel cells supply power for the vehicle which has a gross weight of four tons. In each cell hy-

drazine is combined with oxygen from the air to produce 5000
watts of electricity. Unlike batteries that must be recharged
periodically, cells produce electricity as long as they are supplied with fuel, much as an internal- combustion engine runs
as long as it receives fuel. Exhaust from fuel cells is harmless water vapor and nitrogen. Power from the cells feeds a
3900 -rpm d.c. series traction electric motor through a solid state voltage controller. The motor provides the equivalent of
about 27 horsepower, and replaces the regular 94 horsepower
gasoline engine. Cells were developed by Monsanto Research.
Video Disk Records Color TV. (Center) The model's face is
reflected in the highly polished metal disk used to record color television pictures in a new recording system. The disk is
able to record and play back 30 seconds of action in high -band
color, and any part of the recording may be cued for on -theair use in four seconds. Designed primarily for use in televising sports action, the new system may also be used for rapid low -cost production of color commercials and special -effects
material. Capabilities also include reverse -action playback
at either normal or slow- motion and frame -by -frame advance for animation or analysis of highlights. Rapid playback
of recordings is made possible by use of rare metal disks
with extremely long life instead of conventional reels of tape.
Disk recordings may be mixed with tape and film recordings
in production. Ampex developed system at the request of ABC.
Road -Surface Profiler.

(Left) Precise measurement of road surface profiles is the purpose of the new road profilometer
shown here. Consisting of a light truck modified to accommodate sophisticated electronic instrumentation and measuring
equipment, the profilometer uses two trailing wheels (one at
each side of the truck as shown in the upper photo) to sense
changes in the road's profile. Instrumentation in the truck (lower photo) converts this information into a permanent record on
magnetic tape or a strip chart. General Motors engineers use
the taped data as input for vehicle testing devices in the laboratory, simulating actual road surfaces. Highway engineers also
find the data helpful in checking the effects of aging on road
surfaces and in planning safer highways. The Texas State Highway Department has already purchased one of the instruments.
24

www.americanradiohistory.com

ELECTRONICS WORLD

Rainbow Liquid Laser. (Right) Scientists have developed a
simple liquid laser which can produce a rainbow of different
colors. So far green, yellow, orange, and red laser light have
been produced, and in principle it should be possible to produce all wavelengths in the visible and infrared spectrum. The
color of the beam is changed simply by refilling the liquid
laser with different solutions of organic dyes. In the multiple exposure photo, the laser has been filled with three organic
dyes producing green, yellow, and red laser light. The beams
were separated by rotating a prism in the path of the laser
beam. A special wide -spectrum flash lamp is the pumping
source in the experimental laser which was developed by IBM.
Two -Passenger Electric Car. (Center) Westinghouse has an-

nounced that it is manufacturing a two -passenger electric vehicle called the "Markette ". Powered by 12 six -volt lead -acid
batteries, the small car has a top speed of 25 mi /h and a range
of 50 miles between chargings. The company is producing only
a few hundred of the vehicles which are expected to be purchased mainly by community developers, electric utilities, and
government agencies for experimental purposes. Batteries
should last for at least two years before they need replacement at a cost of about $300. The "Markette" weighs 1730 lbs
including batteries. It is driven by two 41/2- horsepower d.c.
motors. A retractable power cord is plugged into a 117 -volt
outlet for recharging. Price is expected to be under $2000.
Large -Scale Integrated- Circuit Array. (Below right) A universal
4 -bit shift register containing the equivalent of 175 components on a single 60 by 85 mil chip is shown here. This IC,
produced by Sylvania, is the most complex single chip produced by this company. The new register is a true universal
logic element and not just a storage element and is designed to

simplify digital system design. Incorporated in a computer,
each of the new units replaces eight devices formerly needed.
Low -Cost Weather Photos From Space. (Below left) A new
low-cost ($3500 to $5000 depending on accessories) weather
satellite picture taker is now available. The system is within
the reach of colleges and schools, small weather stations in
remote areas, countries with an interest in space research,
ships at sea, and commercial organizations interested in obtaining up to 15 high -resolution cloud -cover photos per day
from our ESSA and Nimbus meteorological satellites. The satellites, in polar orbit, are within range of a given location on
earth for three passes a day. Photos are displayed on a high resolution CRT which is then photographed on Polaroid film.
The system is available from Electro- Mechanical Research, Inc.

July, 1967

Electronic Challenges
in the SST Program
By JOSEPH H. WUJEK,

Jr.

Flying faster than twice the speed of sound, and requiring close control
of flight conditions for passenger safety and comfort. the SST will use
vastly more complex and reliable electronics system than presently used.

HE decision by the United States to proceed with
the development of the supersonic transport (SST)
holds the promise of a significant advance in transportation. In competition for the basic airframe, the Boeing
Company design proposal was chosen, while in the engine
competition, General Electric was selected. Although the
panel of government experts took several months to painstakingly review the detailed proposals, it is impossible at
this time to anticipate all the technical problems which
will arise and require solutions. In this article we shall
examine some of the more obvious difficulties, focusing particular attention on those which may be solved by electronic
systems. As we shall see, the problems will indeed provide
a challenge to our electronics industry.

The SST
To place these problems in a frame of reference, it will
be useful to gain some background in the SST -what it is
and what it hopes to accomplish.
Each Boeing B -2707, as the SST is designated, will cost
over $35 million. For comparison, two of the familiar DC -3
aircraft cost about $50,000 in 1950, while the jet engines
for the SST are expected to cost $50,000 each. A typical
DC -3 carries electronic systems which cost about $12,000,
while each SST is expected to contain about $400,000 in
electronics. It is estimated that the SST program will provide employment for more than 650,000 people over the
next 18 years. These employment figures include all the
support activity required to develop, build, test, and operate
the aircraft, as well as those personnel involved in airport
preparation, etc. Since it is anticipated that world airline
traffic will increase fivefold between 1966 and 1980, a large
segment of the traveling public is expected to benefit directly from this venture.
The airplane will have a useful life of approximately

50,000 hours, which at the projected rate of 3000 hours in
the air each year means about 17 years of operational status. In 50,000 hours of SST operation, the aircraft will
have traveled about 90 million miles, based upon the cruising speed of 30 miles per minute or 1800 miles per hour.
The B -2707 is a huge aircraft, as shown in Fig. 1. With
a length of 306 feet, the SST is longer than the distance
between the goal lines of a football field. The maximum
height of 48 feet, measured at the vertical stabilizer, is
roughly equivalent to that of a five -story building. Each
engine and associated pod is nearly as long as a DC -3 transport. The aircraft in fully loaded configuration will weigh
675,000 pounds, of which 367,100 pounds will be fuel. The
fuel capacity of the SST is thus approximately equivalent
to that of three railroad tank cars.
The aircraft is to be powered by four General Electric
GE4 engines, each developing about 60,000 pounds of
thrust. This power is a significant increase over the 20,000 pound thrust engines in use on commercial transports today.
With a cruising speed of Mach 2.7 (2.7 times the speed
of sound at the altitude specified) or 1800 mi /h at 60,000
feet, the B -2707 will have a range of over 3700 miles under
full load (farther under less load). Depending upon the
seating configuration (first class, tourist, or mixed), the airplane can carry up to 350 passengers.
Table

Comparison of flying times for modern jets vs

Route
New York -London

Modern Jet

SST.

SST

2 hrs., 30 min.

6 hrs., 9 min.

New York -Los Angeles 4 hrs., 40 min.

hr., 50 min.

San Francisco -Tokyo 11 hrs., 35 min. 4 hrs., 45 min.

iLECTRONICS WORLD

www.americanradiohistory.com

The ability to vary wing sweep will allow the aircraft
to take off and land with the wings swept forward, giving
the airplane characteristics not unlike those of today's jet
transports. For high -speed cruising, the wings will be swept
back to the familiar delta configuration, which means less
drag at supersonic speeds.
To appreciate more fully what the SST will mean in terms
of travel convenience, refer to Fig. 2, which is a typical
flight profile for the aircraft. Altitude is shown as a function
of nautical miles (NMI ) The distance of 3800 NMI is
roughly equivalent to a trip from New York to London, or
from Chicago to Honolulu. The M numbers refer to speed
in Mach numbers; hence the cruising speed is Mach 2.7, as
shown in the figure. The time for the entire trip will total
about 23 hours. Table 1 compares flying times of today's
jets with those of the SST for three important cross-country

a9 3"
I.._._..

MAX. RAMP WEIGHT
OPERATING EMPTY WEIGHT
FUEL CAPACITY

MAX. LOG WEIGHT

.._--

123'2"

305

675,000 Ib
287,500 Ib
367,100 Ib
430,000Ib

174'3"

and transoceanic routes.
Now that we have gained some insight into what the SST
is all about, let's examine in detail some of the problems
facing our electronics technology.

105'

Electronic Challenges

Fig. 1. Longer and wider than a

We might begin our discussion with a very common but
nonetheless important element of nearly every electronic
system -wire. Thousands of feet of wire will distribute
power and transmit signals to virtually every portion of the
aircraft. Since the temperature of the aircraft's skin will
rise to over 450° F, wiring exterior to the passenger cabin
and baggage -hold may be exposed to high temperatures.
Moreover, such wiring will undergo many hot /cold cycles
and must not become brittle and break under these stresses.
If it were not for the weight penalty, ordinary industrial
boiler -room wire might fill the need. But a sophisticated
aircraft can hardly be weighed down by bulky wiring. One
solution may be found in the use of the new lightweight
polymer plastics used for insulation. These plastics can
withstand high temperatures and are extremely flame-retardant. Recently developed for aerospace use is a coaxial
cable weighing one ounce per foot and capable of withstanding temperatures 1100° F. Related to this hot /cold
cycle problem is the task of providing motors and servos
which can also survive this environment.
A more difficult research and development problem is that
of automatic control, or the automatic pilot, for the SST.
True, autopilots for both military and commercial aircraft
have been in existence for many years, and nearly all cornmercial transports are so equipped. But the SST poses new
problems for the autopilot designer.
"Dead time," or the time between the sensing of a needed
correction and the full implementation of the correction,
must be reduced. At supersonic speeds, the shortcomings of
an autopilot system are magnified. Just as the driver of a
racing car must be more alert to the task of control at 150
mi /h than at 30 mi /h, so too the autopilot must be more
"alert" as operational speeds increase. A system which is
adequate for a military aircraft where crew personnel may
be required to undergo a rough ride is not acceptable for
commercial operation. A slowly reacting autopilot might
impart a wave -like vertical motion (pitch) to the aircraft
at Mach 2 plus, with a resultant altitude vari,ition of one
hundred feet or more. Few passengers would be willing to
take a roller- coaster ride such as this, no matter how fast
they could span the nation.
Several electronic systems in use and /or undergoing development find application in the SST as well as in contemporary aircraft. Distance measuring equipment ( DME ) is
already standard on most airlines. DME provides the pilot
with precise information as to the distance and rate of closure
to the DME station. This system takes on added importance
in the SST, since flight -plan decisions must be made with a
minimum of delay. With the ever -growing density of air traffic, new demands tvill be placed upon DME. Each station

football field, as tall
building, and weighing nearly 338 tons,
(Boeing B -27071 will carry up to 350 passengers.

as a five -story

the

SST

70
M 2.7
M 2.5

M2.7 CRUISE

Z 60
Ó

M2.7

M1.5

7
F-1

1.3

2.0

M1.5

M1.0

M1.3

2.0

M2.5

1.0

TAXI WEICHT 675,000 lb

o
R

Fig. 2.

SST

4NGE,

NMI

flight profile shows it cruising at Mach 2.7.

must be capable of handling more traffic ill its region than
is presently possible.
With the increase in air traffic, the danger of aircraft
collision becomes ever more acute, particularly in the air
space near major terminals. A collision avoidance system
( CAS) is thus required to insure the safe passage of air
traffic under all conditions of visibility and turbulence.
Ideally, a CAS measures position and rate of closure between
aircraft occupying a given region and warns the pilot of the
collision course. A more advanced system might also transmit collision- avoidance courses to the aircraft heading for
trouble and perhaps even automatically correct to a safe
beading. Several mid -air crashes and near- crashes over the
past few years furnish a grim reminder of the need for a

dependable CAS.
Another cause, or at least a suspected cause, of aircraft
mishaps is clear air turbulence (CAT) The nature of CAT
is not well understood, except to note that this weather
phenomenon can quickly alter the altitude of an aircraft,
placing heavy demands on the autopilot and /or the pilot's
ability to control the aircraft. Severe buffeting may result,
which may in turn trigger structural failure of the airframe
or cause the airplane to go out of control. Electronics may
provide the key to understanding and avoiding this hazard.
Radar and lasers have been suggested as possible tools in
this area of research.
Still another problem which sterns from the continued
increase in air traffic is that of all- weather flying. The
grounding of planes due to weather (Continued on page 7-1)

July, 1967

www.americanradiohistory.com

ONE -TUBE

LOW- FREQUENCY
CONVERTER
By K. H. SUEKER, W3TLQ
Westinghouse Electric Corp.

Construction of ci single -tube converter operating from
15 to 2000 kHz for use with receiver tuned to 10 meters.
NYONE who has listened to a short -wave receiver is
we11 aware of the vagaries of high -frequency radio
transmissions. While average propagation conditions
can be predicted with reasonable certainty, high- frequency
circuits are still plagued by erratic signals and sudden blackouts. Only with the advent of synchronous satellites has
dependable high -frequency transmission over long hauls become a reality. The terminal equipment required, however,
is rather cumbersome.
The glamour of the satellites and the space age has tended
to overshadow the less known but vitally important v.l.f.
services which have offered dependable, world -wide communications for over forty years. Operating on frequencies
from 15 kHz to 30 kHz, super-power transmitters handle a
steady flow of press, naval traffic, and special services. Since
propagation is entirely by ground wave at these frequencies, there is no sky -wave interference and no dependence
on ionospheric conditions. The v.l.f. waves hug the earth's
surface and can cover the entire globe.
The author's interest in v.l.f. 'was stimulated by articles
describing the 2000 -kW installation of NAA at Cutler,

Maine. AVorkbench experiments using a Wien -bridge audio
oscillator as a regenerative detector proved successful at receiving NAA so the decision was made to build a good receiver for v.l.f. Since a faithful general- coverage communications receiver had just been retired, a second objective was
to provide broadcast and 160-meter amateur band coverage
as well as v.l.f. This meant that the receiver had to tune
from 15 kHz to 2000 kHz -a 133 :1 frequency ratio.

Circuit Design
Such an extreme range posed some interesting design
problems. A simple regenerative receiver could handle the
v.l.f. but could not provide the selectivity needed for broadcast reception with strong local stations. Adding tuned r.f.
stages would improve selectivity but would impose difficult
ganging problems to say nothing of requiring a lot of large
inductors. A fixed i.f. superheterodyne offered much the
same sort of problems.
The solution, surprising in its simplicity, was to use a
single -tuned input circuit feeding a converter stage with
fixed oscillator and tunable i.f. This arrangement allowed
R1- 470,000 ohm,

Fig. 1. Schematic and parts list for the one -tube converter.
The triode section of the 6Ú8A serves as a crystal oscillator
whose output is applied to cathode circuit of mixer section.

R2 -1000 ohm,
R3 -3300 ohm,

+125V, I0mA

H. F. ANT.

r
RCAVR.

L F.

ANT.

NT.

\
LI

1.5

ELL
TIIc
I

SWITCH POSITIONS(SI)

I- IS -60kHz

2- 70-200kHz
3- 200-700k Hz

4- 700-20001Hz

our
V

,^\
-4
I

1/2

R4- 100,000 ohm, t/2 \V res.
Cl -See text
C2 -Dual variable capacitor,

467 pF /sec
C3 -0.005 µF ceramic capacitor

C4, C5, C8-0.05 pF ceramic capacitor
C6, C7, C10 -3.30 pF trimmer
C9 -0.1 µF paper capacitor
L1 -65 -300 mH adj. tapped coil (J.W. Miller 9018)
L2 -520 mH adj. tapped coil (J.W. Miller 9015)
L3- 0.5 -3.5 mH adj. tapped coil (J.W. Miller 9013)
L4- 0.15 -1.0 mH adj. tapped coil (J.W.
Miller 9012)
L5- Ferrite -core antenna (see text)
L6, L7 -12 t #22, 3/e" dia. x 5/6" long
L8 -1 t. on cold end of L6
L9 -1 t. on cold end of L7
L10 -1 t. on L7 (see text)

S1- D.p.6 -pos. non -shorting sw. (Mallory 2226J)
S2-D.p.2 -pos. non -shorting sw. (Mallory 3222J)
Xtal -28 -MHz overtone crystal
V1 -6U8A

528

Tyyy

M-

W res.
W res.
W res.

t/2

1/2

6.3V
I

ELECTRONICS WORLD

www.americanradiohistory.com

the use of a high -stability communications receiver as the
tunable i.f. so that a constant tuning rate, selectivity, and
stability could be maintained over the entire 133:1 frequency range.
The schematic for the converter, as it finally evolved, is
shown in Fig. 1. The incoming signal is passed by a tuned
input circuit which covers 15 kHz to 2000 kHz in four
switch -selected, capacitor -tuned ranges. The tuned input
circuit provides image rejection and minimizes cross -modulation by local broadcast stations.
The triode section of the 6U8A is a tuned oscillator which
provides 28 -AIHz output from a third -overtone crystal. Output from the oscillator is coupled to the cathode of the
pentode section and mixed with the 15 -2000 kHz input signal. The resultant mixer output of 28.015 MHz to 30.000
MHz is fed into the input of the communications receiver
«hieh supplies the tunable i.f., detection, b.f.o., and audio
functions.
A few comments on the circuit are in order. C1 -L5 corn prise a rejection trap which can be used to minimize interference from any one especially strong local broadcast station. Cl is chosen in the range 10 -400 pF to allow resonance
within the adjustment range of L5. L1 to L4 are standard
adjustable tapped coils selected for high "Q" and reasonable
cost. Because of multiple resonances in the coils, several of
them will tune two different frequencies at the same setting
of the tuning capacitors. This feature is used to cover the
range with just four coils. Approximate coverage of each coil
is 15 -60 kHz for L1, 70 -200 kHz for L2, 200 -700 kHz for
L3, and 700 -2000 kHz for L4.
Capacitor C10 allows the crystal to be "pulled" to 28.00
MHz for calibration purposes. L10 provides some out -ofphase signal to reduce the 28 -MHz feedthrough to the receiver. A vacuum tube was used in preference to transistors
so that a.g.c. could be used from the communications receiver. If a.g.c. is not used, the converter a.g.c. lead should
be connected to a variable negative -voltage source to pre vent overloading on strong signals. A one- megohm potentiometer across a 9 -volt battery will serve the purpose.
The converter is designed for a high -impedance antenna.
Any practical antenna at the low frequencies is a small fraction of a quarter -wave since a wavelength at 20 kHz is 9.3
miles! Capacitance to ground in the lead -in must be kept to
a reasonable minimum. Coax cable can not be used. The
antenna must be brought directly to the converter. As for
antenna length -the longer the better in this case.

desired frequency (dial indication minus 28 MHz) and the
converter tuning is peaked for the maximum signal.

Stations Received
The spectrum below 2000 kHz is alive with signals and
the converter has enough sensitivity (when used with a
good communications receiver) to perform surprisingly well
with a short antenna. Station GBR in Rugby, England has
been received at the author's Pittsburgh location using only
a 30 -foot vertical antenna. Incidentally, inquiry to the General Post Office in London revealed that GBR has recently
been rebuilt and now operates with a transmitter power output of 500 kW. The 16 -kHz frequency is accurate to 5
parts in 10' °. This historic station went on the air on January
1, 1926 and had, at the time, the highest power vacuum tube amplifier in the world.
Other v.l.f. stations include NAA, NPG, and NSS, all of
which handle Navy traffic. WWVL on 20 kHz and WWVB
on 60 kHz provide standard frequency broadcasts from the
Bureau of Standar ds' new transmitter site in Ft. Collins,
Colorado.
The range 200 -400 kHz is used for low- frequency aircraft
direction -finding services. The low -power transmitters can
be heard within a radius of 100 miles daytime and 1000 or
more miles at night. Detailed aviation weather forecasts are
broadcast in voice from the larger cities. Frequencies
around 500 kHz are used for marine traffic and 500 kHz
itself is reserved as a calling and distress frequency.
The advantages of tuning the broadcast band with a good
communications receiver are quite striking. With this converter, the author has received Radio Belize, British Honduras on 834 kHz with 50 -kW domestic stations on 830 and
840 kHz. Numerous Mexican, Canadian, and Cuban stations
can also be heard.
In the region above the broadcast band, marine navigation beacons, loran, and the 160 -meter amateur band are
available. Amateurs who want to add 160 -meter coverage
to restricted -range communications receivers can build this
converter and get the other services as a bonus.
For amateur operators fed up with QRM, SWL's feci up
with Radio Moscow, or those who are simply in search of
something new, this converter can provide a lot of listening.
There is always something doing from 150 meters down! A

Construction and Adjustments
The entire unit is built in a 3" X 8" X 6" cowl -type
chassis box. No special precautions need be observed in wiring except to keep the high- frequency leads reasonably short.
Coils L6 and L7 are wound on short lengths of 3/8' diameter
polystyrene tubing and supported on their leads. The high frequency antenna and receiver antenna lead should be
brought in through coax to minimize 10 -meter amateur
pickup. The low- frequency antenna can be brought in on
ally convenient type of binding post. The front panel of the
unit may be marked with suitable decals or pressure- sensi-

Entire unit

Single tube

is
is

built into

6" cowl -type chassis box.

horizontally mounted behind the tuning capacitor.

tive labels.
Initial adjustments of the converter are quite simple. C7
is first set so that the 28 -MHz output is slightly below maximum and the crystal oscillates every time when power is
turned on. C6 is peaked for maximum converter output on
v.l.f. signals. The polarity and coupling of L10 to L7 is adjusted for minimum converter output on 28 \IHz. Coils L1
to L4 are peaked on noise (with the antenna connected) at
the low- frequency ends of their respective ranges with C2
at maximum capacitance.
Note that tap connections to L3 are different from the remaining coils. In each coil, however, the end with the greater number of turns (top of winding in diagram) is connected
to S1ß. In use, the communications receiver is tuned to the
July, 1967

www.americanradiohistory.com

ELECTRONIC STETHOSCOPE and
CARDIAC RATE METER
By A. L. DUNN, R. N. WILGER, and R. A. MYERS
Veterans Administration Hospital, Omaha, Nebraska

Using this electronic stethoscope, the

physician can hear the heartbeats and
also observe the cardiac rate on a meter.

Fig. 1. Electronic stethoscope
(left); calibrator on right.

THIS

article describes the construction of a transistorized,
battery- operated unit about the size of a pocket transistor radio which incorporates all the features of earlier
stethoscopes with the addition of a direct -reading heart rate meter.
The photograph ( Fig. 1) shows the general aspects of
the instrument svith the calibrator at the far right. The
circuit of the instrument, 'hier) is based on a five-transistor amplifier (available from Lafayette Electronics under
catalogue number 99 -R- 9037), is shown in Fig. 3. The
combination of R1 and Cl serves as a tone control to
vary the frequency accepted by the amplifier. The gain
control (R16) is located at the output of the amplifier. In
this condition, the amplifier is running "wide open." Points
"A" and "11" connect to "A" and "B" on the rate meter
(Fig. 2) directly, while points "A" and "C" connect to the
headphone system. The original gain control as shown in
the diagram supplied with the commercial amplifier was
taken out, and a 10-p.F capacitor is used to couple transistor Ql to Q2.
The microphone which serves as the pickup device was
constructed from an Air Force type HS -30 headphone. The
case was ground down to the point where the diaphragm

was separated fion) the pole pieces by no more than
the thickness of a piece of tissue paper. This greatly increased the sensitivity. The low impedance of the microphone was a passable match for the input to the amplifier.

(Continued on page 87)
D2

200

ohm potentiometer

R5- 100,000 ohm resistor
R3- 220,000 ohm resistor
R4, R8- 10,000 ohm resistor
R6- 560,000 ohm resistor
R7 -1000 ohm resistor
30
R2,

119-27,000 ohm resistor
R10- 270,000 ohm res.
R11, R14 -330 ohm res.
R12 -3300 ohm resistor
R13 -6800 ohm resistor
R15 -10 ohm resistor

Or.

R1 -1500

ohm resistor

R2, R4-2200 ohm resistor

R3 -2000 ohm potentiometer
R5 -4700 ohm resistor

R6- 20,000 ohm pot.

(All resistors /2 watt.)
C1, C2 -450 5E, 6 V cap.
D1, D2, D3 -10 V zener diode

Q1 -2N170 transistor

TI- transistor

inte stage

trans. (Argonne AR -153

or equis.)
MI -500 5A meter

Fig. 2. The rate meter is transformer -coupled to the stethoscope and accepts pulses which are read out on the meter.

Fig. 3. Schematic and parts list for the electronic stethoscope. This

R1 -500

amplifier

similar to the Lafayette 99 -R -9037.

R16 -200 ohm pot.

(All resistors 1/2 watt.)
C1, C11 -5 5F, 10 V capacitor
C2 through C7 -10 pF, 10 V cap.
C8 -50 5F, 10 V capacitor
C9 -5

F, 10 V capacitor

CIO -0.05 50F, 25 V

capacitor

T1- transistor input trans.
T2- transistor output trans.

QI, Q2, Q3- 2SB113 or equis.
Q4,

Q5- 2SB165

Rr- Lafayette

or equiv.

32S

thermistor

ELECTRONICS

www.americanradiohistory.com

WORLD

Solid -State Circuit Breaker

Operates Within Microseconds
By STANLEY W. THOMAS /Lawrence Radiation Laboratory, Univ. of Calif.*

This electronic circuit breaker operates within microseconds
of initial appearance of a possible damaging short circuit.
may be too slow for adequate short- circuit or overload protection for expensive hi -fi power output stages
and power supplies in the event of accidental shorting
of the speaker leads. The solid -state circuit breaker to be described is a 2.4- ampere device that opens in 2.5 microseconds
under a 4.8- ampere load (100% overload) A simple change
in a resistive shunt permits any desired trip from 10 mA to
more than 10 amperes. The addition of a capacitor will
provide a "slow- blow" characteristic.
The basic circuit is shown in Fig. 1. R1, the sensing shunt,
is made from #20 Ylanganin or Nichrome wire and must
be formed in a non -inductive manner to prevent current
surges from accidentally firing the circuit. A parallel combination of carbon resistors may be used in place of the wire.
Although the circuit was designed for 28 -volt operation, it
can be modified for any supply voltage.
Operation is as follows. Resistor R3 is selected to provide
current to saturate Q2 for a collector current equal to the
trip current. Al'hen an overload occurs on the output side,
the voltage drop across R1 cuts off diode D1 and allows the
current through R2 to flow into the gate of Ql. This fires
the SCR which now shunts the base chive current for Q2,
turning Q2 off. This removes the voltage from the output.
Simultaneously, the "Overload" lamp glows. The SCR (Q1)
is held in conductance by the current through R3 and the
lamp current. Removing the supply voltage (operating the
"Reset" switch) extinguishes Q1 and resets the circuit.
If the lamp indicator is not needed, it may be removed
and D2 and D3 replaced by a conductor.
Diode D1 protects the gate of Q1 from high surge current,
temperature-compensates the circuit, and permits the use
of a capacitor (C1) to form a firing delay. Fig. 2 shows the
effect of Cl on trip time when the load current exceeds the
trip current by 10 %. Diode D2 compensates for the D3 voltage drop and permits the use of the indicator lamp. Diodes
D4 and D5 permit positive shutoff of Q2 by providing a
barrier voltage greater than the "on" voltage of Ql. Fig. 3
FUSES

illustrates the effect on trip time of excessive currents.
A 2N3055 can be substituted for the 2N3716 (Q2). This
will slightly increase the trip time. For trip currents of three
amperes or less, a 2N3054 may be used. A 2N3053 can be
used if the trip current is less than 0.5 ampere. In all cases,
Q2 should be heat-sinked.
Any silicon diode, such as the 1N4001, can be used for
D3, D4, and D5. Any not- too -leaky small germanium diode
(1N270, for example) can be used for Dl. Diode D2 should
be silicon and have a reverse voltage rating greater than
the supply voltage. A 1N4001 can be used to 50 volts, while
a 1N4002 can be used to 100 volts.
SCR Q1 may be any low- current device (about 0.5 to 2
amperes) having a breakdown voltage greater than the
supply voltage. The 2N2329 costs about $21, while the C6ß
(G -E) costs about $2 and has a 200 -volt rating. For 100 volt circuits, a C6A ($1.87) may be used.
"Work performed under auspices of U.S. Atomic Energy Comm.
3.0
I

2.0

01=2N232

I.0

.01=C68 (G-E)
5

446.

.05

.04

"fuse" operates within microseconds
short circuit. Capacitor Cl is added for "slow- blow."

Fig. 1. The solid -state

.03

.02

RESET

28V

IOO

OVERLOAD
LIGHT

50011

#327

120

140

TRIP TIME

160

200

220

240

260

280

Fig. 2. The effect of Cl on trip time when the load current exceeds trip current by 10%. This is extra feature.

Fig. 3. Trip time vs load current for

two different SCR's.

FA8

V5UP

180

-Ils

CURRENT LIMITED BY 02
SATURATION RESISTANCE

FAB

r__,_,

05
FA8
OI=C6Bl3 -E1

02
2N3716

+2N2329

HEAT SINK)

(NOTE

NOTES:

1722 4A

-RI= 0.25
=4k20

2- SELECTED

GAGE MANGANIN WIRE
FOR TRIP DELAY (SEE

TEXT)

July, 1967

fi
10

TRIP TIME -As

www.americanradiohistory.com

INDEPENDENCE HALL

RECONSTRUCTION
SOUND SYSTEM
By

J. PETER NELSON /Ampex

Corporation

Description of 14- chancel tape system that
carries dialogue, sound effects, and switching signals to recreate a historical setting.

1+rLNt 111 N,N, ..

l..7P7r:

ABRICK_BY -BRICK reconstruction of the original Independence Hall in Philadelphia was dedicated on

July 4 last year and opened to tha public. Located
at Knott's Berry Farm, some 40 miles southeast of Los
Angeles, this building houses a unique electronic exhibit
that dramatizes the important events surrounding the
signing of the Declaration of Independence.
The exhibit, set in a reconstruction of the assembly hall
where the historic document was signed, relies primarily
on the power of sound to recreate the historic aura of the
spirited discussions and conversations that attended the
original event. Tables, chairs, candles (electric), ink stands.
and other memorabilia of the period serve as visual focal
points for the program and set the mood for the audio

presentation.
Spectators in tour groups sit along one side of the 40foot- square room, roped off from the exhibit area. A pretty
girl in colonial dress, the tour guide, turns a key in a door
casing, and the show begins.
The house lights dim and the electric candles on the
delegates' tables flicker to life. The audience is transported
in imagination to the 1770's as the 56 delegates to the
Second Continental Congress are heard entering the room
and walking through the audience and on to their tables.
Chairs scrape, men talk and laugh, and papers rustle. John
Reconstruction of 40' by 40' room where Declaration of Independence was signed. The chair in the right background beneath the ornamental arch is a replica of the "rising sun"
chair used by John Hancock, president of the Continental Congress. Speakers are installed under tables, in wall panels,
window casements, and fireplaces for effective stereo illusion.

M..

....;.

Hancock, President of the Continental Congress, raps his
gavel for order and recognizes Richard Henry Lee as the
first speaker.
During the presentation, a battle rages outside the building, a marching hand tramps past playing "The White
Cockade," the town crier proclaims the surrender of Yorktown, and the Liberty Rell tolls. As John Adams delivers an
impassioned speech, the audience hears him stand and
walk in ghostly fashion from one side of the room to the
other.
This histrionic Nvizard y is accomplished with an elaborate
audio system called "Stereo -Rama Fourteen" by its creator,
Philip Stuart, Hollywood producer of documentary films
and exhibits. Stuart has placed 56 (coincidentally, the
number of delegates) James B. Lansing speaker systems
throughout the exhibit room to give depth and presence to
his special effects. They are located under delegates' tables,
in walls, and in window casings and fireplaces.

The Tape System
The heart of the system is a pair of Ampex AG -300 solid state professional audio recorders modified to handle one inch -wide, 1.5 -mil magnetic tape and to provide 14 channels
of signals. The machines run at either 71 or 15 inches per
second. Ten of the channels carry dialogue, three are used
for special sound effects, and the final track controls the
room lights, candles, and audio special effects switching
from speaker to speaker.
The program was recorded in the room where it is presented. Stuart gathered more than twenty famous voices
from radio, motion pictures, and the Broadway stage to
portray the voices of history. These well -known voices add
a dimension of familiarity to the stereo program.
All of the actors gathered in the assembly hall for ten
live recording sessions over a period of six weeks. Acoustical flats on their tables cut clown on bothersome crossfeed.
Footsteps, rustles, and chair -scrapings were recorded as
they took place. The final effect is a blend of these sessions,
with the special effects, outside noises, and control track
added later.
The tape equipment is rack- mounted in the spacious
projection room of the building's second-floor movie theatre.
In the original building, the space was rarely used until
32

www.americanradiohistory.com

ELECTRONICS WORLD

toward the beginning of the 20th century, tveen a museum
was installed complete with stuffed birds.
To provide duplicating and standby capacity, one unit is
a record /reproduce machine and the other is a reproduce

only. The recorders are used on alternate days, leaving the
extra unit for standby. This combination allows operators
to make their own play copies of tapes from masters and
enables then to change and upgrade the program at any
time.
Each 14 -track tape machine uses seven two -track professional audio- recorder electronic units, modified to include a
muting relay to short line outputs in every mode but
"Play." These units have been transferred to deeper chassis
for more effective cooling ( the units run for 11 hours a

:lay).
The equipment is set up for virtually automatic operation of the entertainment cycle so that a tour leader need
do no more than insert a key in a tamper -proof lock in a
door casement to start the show.
To accomplish this. engineers installed photocell assemblies and memory systems in the control boxes of the tape
recorders. Lights and photocells are mounted in the tape
path. As the tape runs between the cells, they sense transparent leaders spliced at the beginning and end of the program.
At the end of the program, the machine goes into rewind
(approximately one minute is required to rewind the entire
program ) AVllen the beginning of the program is sensed,
a forward relay cues the show up automatically.

One of modified speaker systems located under ten tables in
the Assembly Hall. Theater drivers are used for the middle
and upper frequency ranges along with woofer for desired bass.

Building the Recorders
Building 14 -track recorders posed special problems. The
recorders were modified to take the wider tape by installing
takeup and wind motors with double the normal torque.
Locking -type holddowns were permanently attached to the
assemblies. Wider capstan and reel idlers were added and
longer shafts were made for the capstan assemblies. Heavier
solenoids were used for the capstan idlers and heavy -duty
silicon rectifiers were installed in the transport power supply.
Staggered, optically aligned, fixed azimuth audio heads
with low impedance, 200- micro -inch gaps were designed to
give adequate signal -to -noise ratios from the narrow tracks
and retain good tracking and frequency response. This design also gives minimum crosstalk between channels and
good separation.
Two patch panels (one for each recorder) ) were installed and interconnected so that the output, which normally_ comes from the reproducer, may be jumpered to
lead from the recorder, and the recorder input, which
normally is connected to an external source, may be jumpered to lead to the reproducer.
The automatic control circuit for the visual effects and
audio special effects employs frequency- sensitive circuits
with solid -state SCR switching to control the house lights
and candles and to switch the three audio special- effects
channels to any or all of ten surrounding speakers.
Eight JBL S -4000 solid -state power amplifiers are built
into one rack to handle the fourteen channels at 40 watts
per channel. The fourth rack in the system carries a 14channel monitor system.
In the assembly hall, 38 speakers are built into the
window casings. Six unique speakers are mounted in the
wall paneling, using balsa -wood panels as voice -cone resonators. Two standard studio monitor speakers are mounted
in the fireplace casements and tell modified systems are
located under tables, concealed by tablecloths. These systems use theater drivers for middle and upper ranges and
woofers to give the desired bass quality.
Stuart plans to acid additional special effects to the program, such as candles that flicker when the man at that
table speaks and electric fire in the fireplaces. These effects
will also be acuated by the tape -control tracks.
July, 1967

Close-up view of the modified tape recorder with its 14 -track head
stacks, lengthened capstan and idlers, and hocking holddowns.
The special sound system consists of two modified 14 -track professionaR stereo audio tape recorders along with their rack
mounted preamps. The rack at the extreme left is a monitoring
board while the second rack contains the power amplifier units.

www.americanradiohistory.com

Editor's Note: Recently we have seen integrated circuits
radios, phonographs, and hi -fi receivers. Almost every day more and more IC's are finding their way
into consumer electronic equipment. As a matter of fact,
we expect that many color-TV sets will go directly from
fates to integrated circuits, bypassing the transistor itcd stage altogether. To the purchaser of such equipment, this will mean smaller, cooler, better, more reliable, and ultimately, less expensive products (or else
products with a greater number of features). But what
in TV sets,

will this revolution mean to the service technician? In
the first place, the clays of the tube puller and v.o.m.
prober are definitely numbered. The technician will have
to learn and use a different approach to his servicing
and he will have to employ different techniques. To
help orient his thinking along these lines, and to inform the consumer as well, we are running this important 2 -part article. Part I covers the new functional
approach that must be taken, while Part 2 (next month)
will go into the specific test- equipment techniques.

TROUBLESHOOTING INTEGRATED CIRCUITS
PART

THE FUNCTIONAL APPROACH

By WALTER

BUCHSBAUM and WILLIAM D. HENN

New consumer products are being revolution i,_cd by the erse of IC's. The
service technician will have to upgrade his knowledge and change his test
methods in order to meet the challenge that the new circuits will present.
INTEGRATED circuits first appeared in black -and -white
TV sets last year and have since found their svay into
color -TV receivers, radios, phonographs, and high -fidelity
equipment. Within the next few years IC's will be used in
all consumer electronic products where high power is not required. RCA, one of the leading manufacturers of IC's for
consumer products, has set up a special engineering task
force to develop a color -TV set using only IC's and a few
power transistors. The idea is to eliminate the stage of designing a fully transistorized color set and concentrate on new
circuits and special IC's for all low -power circuit functions.
It may be possible, for example, to provide all color sync
and demodulation functions with only three IC's
The integrated circuits used in consumer products generally fall into the category of linear or analog circuits, as opposed to the digital circuits used in computers. Analog circuits use many more semiconductors but because of the
very small size of the integrated circuit itself, there is usually
no difference in packaging. These IC's invariably work with
conventional discrete components, such as resistors, capacitors, and inductors, which are connected to the IC by the
printed -circuit board.
When troubleshooting equipment using vacuum tubes,
the first step is usually to check that the filament of each tube
is on. The second step is to substitute known good tubes for
'the suspected ones. These two steps eliminate the majority
of defects without test equipment and without requiring
much technical know -how. Where series filaments are involved, or when the defect is not due to a tube, basic voltage
and resistance measurements can usually locate another large
category of possible defects. Sophisticated test equipment,
such as signal generators and scopes, is usually needed only
for alignment, which is rarely done.
In troubleshooting transistorized equipment, however,
this first step -checking filaments and substituting tubes-

"In order to troubleshoot
will raped two basic aids.

the technician
The first is goodquality test equipment capable of dynamic
in- circuit testing. The second is detailed
knowledge of circuit functions and signals."
11 "s

cannot be used and some form of test equipment is needed
immediately to locate the defect. Voltage and resistance
measurements help to isolate the defect to a particular circuit
function but then individual components, including the transistors, must be tested. This is usually done with the power
off and often requires quite a bit of unsoldering of leads. In
many instances new transistors are temporarily connected
into the circuit. For complete dynamic tests of a transistor
a good transistor tester is needed and even this check is not
always conclusive because the temperature effects in the
equipment are not duplicated by the transistor tester. As a
last resort, test equipment, such as signal generators and
oscilloscopes, is required to trace the defect down to the
responsible components.
When it comes to troubleshooting equipment using integrated circuits, voltage and resistance measurements are
often inconclusive and difficult to perform. It is not practical
to unsolder the 10 to 14 leads of the suspected IC and then
solder another IC in place. The d.c. voltages alone often do
not pinpoint the defect and ohmmeter measurements can
damage the IC by applying wrong voltages across semiconductor terminals. The only remaining troubleshooting pro cedure is signal- tracing but this, too, is often limited. As
will be shown later, many IC's contain more than the basic
amplification function and this means that the output signal frequency may be different from that of the input. Even
if signal tracing pinpoints the defect to a particular stage, it
is not easy to determine whether the IC itself or one of the
external components is defective. If the external component
defect has caused the IC to be damaged, troubleshooting can
be extremely difficult.
In order to troubleshoot IC's efficiently, the technician will
need two basic aids. The first is good -quality test equipment
capable of dynamic, in- circuit testing over a wide range of
frequencies, modulations, and waveforms. The second is a
detailed knowledge of the circuit functions and signals in
each part of the equipment, and how they can be examined
under dynamic conditions. The test equipment problem will
be covered in depth in a subsequent article while the functional aspects of integrated circuits will be discussed here.

How Can IC's Become Defective?
Solid -state devices, and integrated circuits in particular,

ELECTRONICS WORLD

The

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approach will be described in further detail in Part 2.

Understand the Function

111'1'

are inherently more reliable than vacuum tubes. They do
not contain a cathode which can wear out, they do not contain the relatively large mechanical structure of the electrodes, nor do they depend on the vacuum. Nevertheless, any
integrated circuit can fail. Most of the reliability and life studies performed on IC's for military applications have concentrated on digital circuits, but the results are equally applicable to analog circuits.
IC defects are classified as those clue to manufacturing
faults, those due to electrical circuit abuse, those due to
mechanical abuse, and those due to undetermined causes.
Fortunately, this last group accounts for a very small percentage of failures. \ianufacturing faults may only become apparent after a few months. For example, internal short
circuits may develop clue to very slow chemical reaction or
because of inadequate passivation. Contamination is another
manufacturing defect which may not show up for months.
Probably the most frequent cause is mechanical abuse in
the equipment assembly process. When individual leads are
stretched tight it may only take a few cycles of heating and
cooling until the internal connection breaks and such breaks
often result in a high- resistance connection rather than a
clear open circuit. Mechanical vibration or shock can, over
a period of time, loosen internal connections until the IC beconies defective. The electrical circuit abuse is usually the
result of some external component failure which produces
excessive voltages or insufficient bias which then damages
the IC.
Technicians cannot spend the time and effort required to
disassemble and microscopically examine the IC to find the
damage. This would be fruitless, in any event, since the IC
cannot be repaired. The technician's aim is to determine
positively that the IC itself is defective and that this defect
is not caused by failure of some other component.

The Pin -Connection Problem
The great advantage of IC's is their small size. At the same
time, however, analog IC's provide a wide range of functions and therefore have quite a few external connections.
The dimensional outline of Fig. 1 shows a typical low -power,
wide -band amplifier %vith 12 separate pins. A small tab opposite the number-12 pin serves as key. The leads are usually
spread out, sometimes by special standoff pads, which separate the IC from the printed -circuit board. Even the spread out leads are still too close together to permit attachment
of even the smallest alligator clip to one lead without touching its neighbor. It is almost impossible to unsolder a single
lead without damage to the rest of the circuit. Even the use
of a miniature soldering iron, with a tip diameter of Iii' is
not much help because it is difficult to pull an individual
lead out through the printed -circuit board.
Fortunately, most of the IC leads are connected to the
external components or to wires and these can be unsoldered,
leaving the printed-circuit board connection as an isolated
terminal of the IC itself. When several components are connected to the printed -circuit terminal, all of them have to be
unsoldered in order to isolate one IC lead. For this reason
tests which require connections to several IC terminals are
very cumbersome and technicians should try to avoid them
if possible.
To eliminate the messy unsoldering usually associated
with getting at the IC pins, techniques are needed which
depend on in-circuit tests and need only a minimum of test
connections. Even these few connections should be made to
the external component rather than the IC itself. The ideal
approach would be one in which test signals are injected and
measured by inductive or capacitive coupling probes. Such

In troubleshooting tube and transistor equipment, the
technician has become accustomed to analyzing the circuit
ill terms of each resistor, capacitor, and inductor so that
he can trace the defects to individual components. If this

sane technique were used

in troubleshooting IC's, considerable difficulty would be encountered. To illustrate, let us
consider the RCA CA -3000 d.c. amplifier, the circuit of
which is shown in Fig. 2. As seen here, the amplifier really
consists of two amplifiers with two inputs and two outputs
and control circuitry that permits a variety of connections.
()3 and diodes D1, D2 and their associated circuitry permit
a variety of controls for one or both of the amplifiers.
The manufacturer's data describes four modes of operation for this circuit with different terminals shorted, different
auditions of the diodes, and different values of emitter
resistance for the control transistor. Without going into
the various modes in which this IC can be used, let us consider a very practical application, that of a 10 -\IHz amplifier, as illustrated in Fig. 3. This amplifier, typical of the i.f.
stages in an F \I receiver, uses a tuned -input and tuned -output circuit and provides a gain of approximately 29 dB.
To test the operation of this amplifier, it is only necessary
to inject a signal, VIN, and then measure the output, Ve, .,..
VIA should be a 10-MHz sine wave of approximately 10
mV peak -to -peak amplitude and V11I y should then be about
30 times that amplitude. This measurement requires a wellleo
MAX.

335
305

230

1.015
DIA

DIA.

e
,3o

370

.335
O

DIA.

018

03éß
045
002 DIA
I. Dimensions (in inches) of typical integrated circuit.
Another commonly used package is the plastic flat -pack, a rectangular case with a number of leads coming out of the sides.
2

Fig.

2. Schematic a nd terminal connections for IC d.c.
this case a ten -pin transistor -like package is

fier. In

ampliused.

VCC(*)

July, 1967

www.americanradiohistory.com

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Fig.

3. Schematic and

106

- MNx

response curve of 10 -MHz tuned -input,
IC shown in Fig. 2.

tuned -output, narrow -band amplifier using

OUTPUT
INPUT

Fig. 4. Equivalent

circuit diagram of
10 -MHz amplifier.

FROM
SOUND DET.

C4.5MHz

DETECTED
INTEGRATED
CIRCUIT

AUDIO

TRANSISTOR
DRIVER
STAGE

TRANSISTOR
OUTPUT
STAGE

VOLUME
I

Fig. 5.

7 -VOLT SUPPLY VOLTAGE

Block diagram showing use of IC in television receiver.

calibrated sweep generator and an oscilloscope capable of
10 mV /cm sensitivity with a detector probe.
If something appears wrong, the technician would then
check to make sure that the correct positive voltage is applied
at pin 9 and a negative voltage at pin 3. Pin 10 must also be
connected to the "B +" and pills 2, 6, and 7 must be at
ground. To analyze the circuit takes quite a bit of doing. We
must translate the schematic diagram of Fig. 2 and the connection diagram of Fig. 3 into the actual equivalent circuit
of Fig. 4. To simplify the circuit of Fig. 2 only the important
elements are shown.
The control circuit composed of Q3 and its diodes and resistors has been lumped together as resistor R -. The functions provided by Q5 and R6 have been lumped together
into R,- and R7. With these simplifications we now recognize a two -stage, emitter -follower (Q1 and Q2) driving
the emitter of Q4. The signal output is at the collector of
Q4. For the sake of simplicity we have omitted the r.f. bypass capacitors and we have connected the output capacitor
C2 directly across L2, which is equivalent to the connection
shown in Fig. 3. We can now analyze the circuit of Fig. 4 in

becomes obrions that an analysis of
the internal circuit itself is of no par tienlar raine in troubleshooting. The
function of the 1C and fnnetions of each
lead are the really essential parts."
e_It

terms of each of the transistors and individual resistors but
since we cannot test them individually or measure their
values, very little has been gained. A defect in any of these
components will still prevent the entire unit from operating
correctly.
Evaluation of the circuit of Fig. 4 and its relation to Fig. 2
does tell us, however, that if pin 4, for example, were
grounded, this would alter the effective value of R. If pin
4 were shorted to pin 3, a typical defect in an IC assembly,
the value of R r would be similarly affected and the over-all
gain would change. If pins 4 and 5 were shorted together,
R r- would again be affected. Pin 6, the input lead to Q5 in
Fig. 2, is grounded for this particular application and if
it were shorted to the ground of pin 7, this would have no
effect at all. If pins 8 and 9 were shorted together, however,
this would be equivalent to shorting out the tuned circuit
load and there would be no output from the amplifier. The
same thing applies if pins 1 and 2 were shorted together,
as this would effectively short out the input tuned circuit.
It becomes apparent that the condition of the ten pins of
the CA -3000 integrated circuit is of much more significance
in troubleshooting than the individual components which
make up the IC. It also becomes obvious that an analysis of
the internal circuit itself is of no particular value in troubleshooting. The function of the IC, in this case an amplifier of
10 MHz, and the functions of each of the leads are the
really essential parts for troubleshooting.
Troubleshooting directions for the 10 -MHz amplifier circuit can simply direct the technician to make sure that pins
6 and 7 are grounded and that none of the other pins is
grounded, that pins 9 and 10 are at +6 volts, and that pin 3
is at -6 volts. The amplitude of Vx and the expected amplitudes of Vo1.... must be given, together with the impedances.
The technician would then check the voltages, measure the
input 10-MHz signal and compare it with the output.
IC pins are quite thin and it can happen that the connection from the printed -board terminal to the IC itself is intermittent or open. The voltage check will not reveal this
since the test leads cannot be attached to the point where the
IC pin enters the IC case. Connecting a signal generator or
scope probe to the tuned circuits without loading or detuning them requires some care. These points will be discussed
in Part 2 of this article.

Troubleshooting the TV Sound IC
To demonstrate how the IC in a typical consumer product
modifies the established troubleshooting procedures, let
us consider the integrated circuit which is used in an intercarrier -sound TV receiver. Fig. 5 is a block diagram of the
RCA Model CTC -21 sound section. From the second detector
the 4.5 -MHz intercarrier sound i.f. goes through a transformer to the integrated circuit. The +7 volts are supplied
to the integrated circuit and the audio- output signal goes
from the IC to the volume control. The transistor driver
stage and the transistor output stage are conventional and
will not be discussed.
Judging by the block diagram of Fig. 5, only four connections must be made to the integrated circuit. In actual practice, however, the interconnections are much more complex.
Fig. 6 shows the detailed interconnection diagram of the
single IC which serves as an amplifier, FM detector, and

audio preamplifier.
It is interesting to compare the functional diagram of Fig. 6
with the actual circuit of the IC itself as shown in Fig. 7. The
IC consists of eight transistors, Q1 through Q8, which perform the i.f. amplification and limiting, and two transistors,
Q9 and Q10, which provide suitable bias voltages, and two
diode assemblies, D1 and D2, which act as voltage dividers.
This section amplifies the 4.5 -MHz intercarrier i.f. signal to
drive the discriminator transformer. The F \I detector and
audio amplifier section consist of the remainder of the IC.
Two diodes, D3 and D4, together (Continued on page 75)
ELECTRONICS WORLD

www.americanradiohistory.com

The author

received his

Cum Laude
from Yale in 1937 and his
PhD in physics from Yale
in 1940. He joined Bell
Labs in 1940 doing research in microwave circuits, switching to microwave tube development in 1944. Since 1948, he has been
concerned with transistor and diode research and development, including varactor diodes and high -speed switching
diodes, microwave protectors, amplifiers, and power
sources. He is currently in charge of microwave transistor development and their fabrication techniques.
BS

'TRANSISTOR selection is

Magna

Selection of Transistors
By R.M. RYDER
Bell Telephone Laboratories

The various types of transistors cover, (1
in this special section are compared with
a view toward making the best selection.

complicated matter. There are literally

1 thousands of type numbers belonging to several different kinds of
construction and operation. In order to understand how their properties

interrelate, some generic properties of different classes of transistors
are discussed in this introduction.
1. The original point- contact transistor was of great theoretical importance in establishing the possibility of bipolar (electrons moving in
one direction, holes in the oppositî direction) transistor action, namely,
the injection and collection of minority carriers. Such minority carriers
are holes in n -type material and electrons in p -type material. However,
from a practical point of view, its properties never were under very good
control; and this transistor has been relegated to the museum by
later types.
2. Grown -junction transistors are also important from the theoretical
point of view since they establish the quantitative accuracy of Shockley's
theory of bipolar transistor action. From the practical point of view,
they have been replaced by alloy junctions.
3. The alloying technique, using germanium, led to the first successful
large -area junction transistors. Their performance is good up to several
megahertz in frequency, and also suffices for power units of respectable
size -scores of watts. The alloy -junction transistor is still in extensive
manufacture.
4. Filamentary transistors (sometimes known as "double -base diodes"), and four -layer p -n -p -n stepping transistors ( "controlled rectifiers") have some interesting special properties but will not be discussed
further here.
5. The diffused -base technique (1956) raised the frequency capability of transistors by orders of magnitude. With increasingly fine control
of electrode sizes as well as diffusion profiles and epitaxial material,
bipolar transistor performance has moved up to several thousand megahertz. The diffusion technique also facilitated the use of silicon rather
than germanium, which helps power capability; and with the development of passivating insulating coatings a very high degree of reliability
can be achieved. With diffusion and photolithography as techniques and
with silicon as a material, the bipolar transistor has developed today's
very wide performance capabilities.
6. Field -effect transistors were proposed even before the bipolar
transistor was discovered, but their operation in a practical sense has
depended upon techniques developed for bipolar transistors. The interplay between these two types of transistors is very interesting and will
be described in some detail.
Up to a few years ago, FET's were not available for the following
reasons. First, FET's would not work at all until semiconductor surfaces
were available which had reasonably low populations of surface states.
Second, even after reasonably good surfaces were available, the performance gain -band product, f,,,:,,, was lower than bipolar transistors by
an order of magnitude. Third, the reliability of FET's was highly questionable. With small input currents, a small change in leakage current means
a fairly large drift in biasing point.
In the course of the past several years, this situation has changed
drastically, again for three reasons. First, surface coatings with much
better and more stable surface characteristics have been developed.
Second, the insulated -gate FE? has been invented. This device, variously
known as the IGFET, MOSFET (me:ai -oxide silicon field -effect transistor),

or MOS transistor, has the gate electrode deposited on top of the insulating coating, thereby exerting field -effect action on the carrier flow
in the semiconductor beneath, without at the same time drawing appreciable d.c. current. This feature is believed likely to lead to flexibility
in applications to monolithic integrated circuits, since the electrodes can
be deposited with protean shapes and sizes. Third, photosensitive methods have been developed for making very fine scale, closely controlled
electrodes on semiconductor devices. These are the same techniques
which have enabled bipolar transistors to operate successfully well into
the microwave region. Even though it is still true that bipolar transistors
are faster than FET's, the latter are capable of useful operation up to
several hundred megahertz. So we have the curious situation that the
FET transistor, which is historically older than the bipolar, has become
practical more recently, and in fact is dependent on bipolar techniques
for its practicality.
At present the broad situation can be outlined as follows. 1. It is
expected that with proper fabrication methods all these types of transistors will be stable for long -term operation even without external protective cans. 2. The bipolar transistor is greatly superior for gain -band
product in broadband applications or for maximum frequency response
such as microwave applications. Bipolar transistors are also higher in
power capability than FET's. 3. FET's have some special advantages, too.
For one thing, the input impedance is high, at least at low frequencies,
permitting high -impedance amplifiers resembling vacuum tubes in behavior. This property is often convenient in such applications as bridging
amplifiers or in working from high- impedance sources. Then, too, the
fact that gain -band product is lower is advantageous to the FET in some
applications. For example, in narrow -band applications such as radio
receivers, for equal gain the selectivity of an FET is better, so that the
receiver can utilize the narrower band to help discriminate against interfering signals. For the same reason, distortion products may be lower
when signals become large.
Noise performance is remarkably good for the best transistors of
either type. However, at low frequencies where 1/f noise is important,
the usual operating points of bipolar transistors tend to be noisy because high current is drawn. Special designs for low noise at low
frequencies should have very low currents and voltages, and special care
should be taken with these surfaces to keep 1/f noise low, although
bandwidth or frequency response may be sacrificed.
7. Integrated circuits. In the future it is expected that to an increasing extent the entire circuit, rather than the transistor alone, will be
buili as a unit. This introduces still other considerations into the choice
of transistors, since fabrication compatibility with the rest of the circuit
enters the picture and there are many possibilities to be intercompared
(monolithic, thin -film circuits, multichips, and many subvariations).
While a discussion of IC's is outside the scope of these articles, it will
be found that a discussion of the properties of transistors is still germane to their performance even when they are used in integrated
circuits.
To sum up, bipolar transistors may be designed to have higher bandwidth, high -frequency response, and higher power. Field -effect transistors may be more selective, have higher input impedance especially at
low Frequencies, and perhaps have some fabrication advantages which
may reduce cost, especially in integrated circuits.

July, 1967

www.americanradiohistory.com

The author received his B.S. and M.S. degrees in Electrical
Engineering from Newark College of Engineering. As a 1st
Lt. in the Air Force he served as Ground Electronics Officer. Upon leaving the service, he joined ITT Laboratories
as a design engineer. Since 1961 he has been a member of
the Computer & Communications Lab at RCA where his
work is primarily concerned with the design of h.f. circuits
for evaluation of v.h.f. and u.h.f. transistors. He is au-

thor of several published papers and

member of IEEE.

Small- Signal
High -Frequency Transistors
By T. J. ROBE
Electronic Components and Devices, Radio Corporation of America

Valuable tips are offered below for selecting radio-frequency
transistors. Included is description of scattering parameters.
\I.AI.I,- signal high -frequency tr:utsistot's

are designed
lo provide high gaits and lost noise at high frequencies. 'fo attain Iltjs, high-frequency transistors
have a very marrow base and small hase -spreading resistance rt,'. Low -frequency (audio) transistors generally
require a very high d.e. beta, higher breal:dottu- voltage
ratings, and low lote -frequency noise. Sns :dl- sigu:tl switching transistors, which :arts also required to have high frequency capabilities, must he designed to minimize
carrier storage in the base and collector regions. III general, the requirements for switching loth- and high -frequency transistors are incompatible and compromises must
be stade to achieve the optimum characteristics for an
intender l :t t,pl ica t ion.
Today's high -frequency transistors have unity- powergain frequencies, f
in the listige from 3(111 \Illz to (i
GHz. \lost transistors which are .suitable l'or small- .signal
high -frequency amplification cats be classified as one of
the following general types:

Table
C,

Ccm
f,`, ,

GM A
GAIS

Gr U

hc
k

ri,'

Su
S,_

S...,

y
Y,y,>

Significant parameters for high- frequency transistors.

Collector- barrier capacitance
Collector -base feedback capacitance
Unity- power -gain frequency (figure of merit)
Gain -bandwidth product (the frequency where ht,. = 1)
Maximum available transducer power gain
Maximum stable power gain
Transducer power gain (unilateral)
Forward current gain with output a.c. short -circuited
Stability factor
Ratio of total transistor noise power delivered to a load to
the noise power delivered to the same load by the source
Base -spreading resistance
Emitter -base dynamic resistance
Input reflection coefficient
Reverse voltage transfer ratio
Forward voltage transfer ratio
Output reflection coefficient
Input admittance
t with output a.c.
Forward current -voltage ratio S short- circuited
Reverse current -voltage ratio t with input a.c.
Output admittance
short -circuited

Silicon planar epitaxial transistors (examples: 2N28.57,

2N:393°2. and 1N 1á6U)

Insulated -gate field -effect transistors which are also
called \IOSFET's (examples: 3N1á8 and RCA Dev. Nos.
T.\ î (11(1, '1':1á(i 1-1)
:3. ,function gate FET's (examples: °N1416, áN3823).
á.

Important Parameters
The significant parameters for high -frequency transistors

are summarized in Table 1. An examination of the internal
transistor parameters which relate to the unity -power -gain
frequency, f ,.,., and to lote noise at high frequency is
facilitated by use of an approximate high- frequency equivalent circuit for a transistor (Fig. 1-A). The circuit describes the diffused transistor chip. exclusive of its pack age, which is applicable at frequencies very near f,,,,,,.

assumed that internal feedback is negligible: this assumption permits the calculation of the frequency at which the
unilateral potter gain is unity. Front Fig. 1A, the following
expression for the trauducer power gaits, G.t.u, under conditions of snatched lone and matched source impedances,
can he derived:

GC°

potter delivered to matched load
potter available from the source

8r rt'

C',.

the unilateral power gain is assumed to be unity,
Eq. 1 cran be rewritten to express the frequency at which
this occurs:
¡
J

- t ains-

')5 rn

'C.

(2)

Eq. á indicates that if a high f,,,,,,. is required, the transistor should have a high gain -bandwidth product fT, a
low base- spreading resistance, rt', and a low collectorbarrier capacitance,
At high frequencies, a high f -,. and a lote r1,' are required
for low noise figure NF, as well as for high power gain
Fig. 113) The manufacturer's data on low- noise, highfrequency transistors normally specifies a minimum value
for .small- signal Its,, measured at a frequency, f, above
(

ELECTRONICS WORLD

www.americanradiohistory.com

the reduction
following relation:
Nvhich

lafe

111

uiQ

with frequency is given by the

= fT' f

(3)

The gain -bandwidth product, IT, can be easily calculated
from Eq. 3.
Although it is difficult to measure rt,' directly, it is relatively easy to measure the rt' C,. product. The parameters
f T and rt,' C. together with the power gain and noise figure, serve as a good initial guide to transistor selection.
Another important parameter in the selection process is
the total collector -to -base feedback capacitance Cr.t; which
provides some indication of transistor stability. This feed back capacitance includes the collector- barrier capacitance Ce, the internal base- contact -to-collector capacitance,
and the stray interlead capacitance of the header.
High -frequency figure-of-merit parameters comparable
to IT and r,' are not generally available for field -effect
transistors. However. power gain and noise figure in a
functional circuit are normally given for FET's which are
intended for high -frequency operation. As will be discussed later, if the two-port parameters are given they can
also be used in the selection.
The figure -of -merit parameters fT and rt; C are related
to the transistor chip only and do not include the effects
o. the package stray reactances, such as series lead inductance and interlead capacitance. The two -port parameters, on the other hand. characterize the total transistor
at the single frequency at which they are measured. From
this standpoint, these parameters paint a better over -all
picture of the transistor performance at high frequency,
especially for operation at frequencies above approximately
10O

JIHz.

In the earlier transistors which had an upper- frequency
limit of about 100 MHz, it was common to find the hor hybrid -pi parameter; in the manufacturer's data because these parameters are relatively easy to measure on
these particular transistors. As the frequency capabilities
of transistors increase to the higher v.h.f. and the lower
u.h.f. ranges, it becomes more difficult to measure these
parameters, because the "hotter" transistors tend to oscillate
with open- circuit terminations. The short- circuit y -paramcters have replaced the h- parameters in the manufacturer's data and are today the most prominent two -port
parameters given for small-signal high -frequency transistors. The short -circuit admittance parameters are very
useful in determining the maximum stable power gain that
can he realized at a given frequency.

Scattering Parameters
High- frequency transistors which are capable of operation at frequencies on the order of 1 (iHz and higher are
available. At these microwave frequencies. the scattering
IS) parameters may be easier to measure than either
the 1i- or y- parameters. Neither an open -circuit nor a
short- circuit termination, both of which are difficult to
achieve in the microwave region, is required for the measurements. Instead, the transistor is terminated by a reference(' impedance, typically 5(1 ohms. which consists of a
transmission line operated into a matched termination. An
accurate termination of this type is much easier to achieve
than the short -circuit termination required for the admittance parameter measurements.
The scattering parameters of a two -port network are
defined in ternis of reflection coefficients and voltage transfer ratios rather than by ratios of the terminal volt ages and currents. For the network of Fig. 2, the scattering parameters are defined as follows:
S11

= Str =

E10

= = input reflection coefficient
O

with the output terminated in

Z,,.

WI' CC

LOG

(A)

(B)

(Al Approximate high- frequency equivalent circuit
for conventional (bipolar) transistor. (B) Frequency at
which noise figure begins to rise depends on f and ri,'.
Fig. 1.

Zp LINE

Zo LINE

--`" ERz

EI,

ERi

Ezz
Z

BOUNDARY OF THE TRANSISTOR
LEADS AS THEY EMERGE FROM
THE HEADER

EZI= INCIDENT VOLTAGE AT THE INPUT
ERI

REFLECTED VOLTAGE AT THE INPUT

E12= INCIDENT VOLTAGE AT THE OUTPUT
ER2= REFLECTED VOLTAGE AT THE OUTPUT

s21

for defining scattering

2. Circuit

Fig.

Sfe

E,..
-

Ett

(S)

parameters.

=0 = forward voltage transfer ra-

tio with the output terminated in Z.

S.0= Soc- -E'

Etl =

= output reflection coefficient

witlt the input terminated in Z.
Sl

_ 1

ft_

F, t

= reverse voltage transfer ra-

do with the input terminated in Z.

Transistor Selection
Military and aerospace applications normally require
guaranteed reliability and environmental capability, with
cost somewhat subordinate. Entertainment applications
tend to emphasize low cost. The reliability of the transistor must also be considered, however, because field
failures in auto radios and TV sets will soon cut into the
set manufacturer's profit. In industrial applications, cost,
reliability, and environmental factors are just about evenly weighted.
The differences in transistor cost are primarily based on
two factors: volume and guarantees in ternis of reliability
and electrical performance. Low -cost entertainment transistors are available because of the high volumes in which
they are produced. High -reliability transistors for military
and aerospace applications are produced ill relatively small
quantities with extensive inspections. burn -ins, and life
tests to guarantee and document their reliability. As a
result their costs are relatively high. In terms of cost
z'ersrts reliability. a transistor from a high -volume production line should be selected if guaranteed reliability is
not required (the word guaranteed should be emphasized
because reliable performance is also required of the high volume transistor) Of course, when transistors which
represent. the limit of state -of- the -art are required in the
application, the cost of these particular devices will be
relatively high.
The choice between silicon and germanium has all but
vanished in the small -signal high- frequency area. The
planar process has allowed the environmentally superior
silicon transistor to equal or exceed the high- frequency
electrical performance of its germanium competitor while
at the same time its cost is low if produced in large volumes.
.

July, 1967

www.americanradiohistory.com

If the transistor is not unconditionally stable, lossy terminations gs and gr, (source and load conductances, respectively) , can be placed at the input and output terminals

so that k = 1. For this condition, the maximum stable
power gain, Gtt5, is given by Eq. 6:
-2.5V

o 0.7V

Vqe

0.9V

0.118

Vbe

(A)

(B)

Fig. 3. Transfer characteristics of (Al FET, (B) bipolar transistor.

Another fundamental choice that must be made is
whether to use a bipolar transistor or a field-effect transistor. If cost is critical, the FET is an unlikely choice
because at present these transistors are produced in much
smaller volumes and, therefore, are more costly than many
high -performance bipolar transistors. Generally, bipolar
transistors also provide somewhat better noise figures
and power gain. The high -frequency FET, however, provides a superior dynamic range and greater freedom from
cross-modulation distortion.
Fig. 3 shows typical transfer characteristics of an FET
and a bipolar (conventional) transistor. The curves show
that the input voltage change from cut -off to saturation
for the bipolar transistor is only about 0.1 volt as compared to several volts for the FET. Although it is not obvious from the curves. the FET approximates a square law characteristic, which is ideal for the reduction of third order nonlinearities that result in cross -modulation and
in -band intermodulation distortion products. The FET
might then be the choice for applications in which low
distortion is very important.
(Editor's Note: For further details on the field -effect
transistor, refer to the article on that subject in this
special section.)
Automatic gain control is an important factor in the
selection of a high- frequency transistor for a stage in
which gain control is required. A dual -gate AIOSFET (e.g..
RCA 1ev. Nos. TA7010, T. ((14) provides both excellent
a.g.c. capability and outstanding cross -modulation performance. Bipolar transistors can also be gain-controlled.
Some types provide reverse a.g.c. (gain reduced by decreasing emitter current) while others are designed to
provide forward a.g.c. (gain reduced by increasing emitter
current) The f T of transistors that have forward a.g.c.
characteristics decreases rapidly when the emitter current
rises above about 3 mA. If the gain -controlled stage is
located in the receiver at a point where cross -modulation
is important, it is preferable to choose a forward a.g.c.
type because cross -modulation distortion in bipolar transistors decreases with increasing emitter current.
The final item to consider is the amount of stable power
gain required. The two -port parameters provide an insight into this capability at a single frequency. The transistor will be unconditionally stable (i.e., no combination
of source and load terminations can be found
will
cause oscillation) at a given frequency if the stability
factor k, defined by Eq. 4, is equal to or greater than unity:
.

='4119,2 -R,.

(y1_ ?/91)

tY1_ Y21

where the y's are conductances and the y's admittances.
For common -emitter operation, g11 = g,,; g_., = y
R.
real
part of the (,yr Jfe ) product; and J1 s Jet
t
a part
12 (yY'21)
= magnitude of the (y,.,. yo.) product.
Under the condition k ? 1, the transistor can be conjugately matched at the input and output terminals, and
the maximum available transducer power gain, G.1/A, is
then expressed as follows:

GuA

Y21

th_

(1,;"-1)'-

(5)

ysi

(6)

Y12

These power -gain expressions are useful for comparisons of high- frequency transistors. The practical transistor amplifier will probably provide somewhat less gain
than the maximum stable value because a safety margin
must be allowed for transistor interchangeability and tern perature changes. In addition, losses associated with the
transformation networks will subtract frosts the amount
of gain that is realizable.

Practical Circuit Considerations
Calculation of the stability factor k shows that the
common-emitter (CE) configuration is unconditionally
stable over a much wider range of frequencies than the common -base (CB) connection. The CE circuit, therefore, is
recommended in most applications because it is much
easier to stabilize. It is for this reason that the manufacturer's data on high- frequency transistors gives CE rather
than ('B y- parameters. When the operating frequency is
sufficiently high so that CE operation does not provide
adequate gain. the CB configuration should be used in
order to take advantage of its positive feedback. This situation. however, does not normally occur until the operating
frequency is higher than approximately 7OÇ of f T.
When a high -frequency transistor stage is designed for
low -noise operation. such as in the first r.f. amplifier of a
radio receiver or the first i.f. amplifier when no r.f. amplifier precedes the converter. particular attention should be
given to the design of the input circuit. Noise figure is a
function of the source resistance R,,, at the transistor input
terminals. At a given frequency and emitter current, there
is am optimum value of R, for low -noise operation; this
value decreases with increasing frequency and increasing

emitter current.
For the transistor in the CE configuration, the optimum
R,5 is normally not much different from the power-matched
source resistance. There is an optimum emitter current for
low -noise operation because the emitter -to -base dynamic
resistance, r., is an inverse function of the emitter current,
/e. For most high -frequency transistors. the optimum emitter current is in the range from 1 to '2 mA. The input circuit
is required to provide the optimum value of source resistance R,,, but must not be lossy because any attenuation
at the input adds directly to the over -all noise figure. i.e.,
an input loss of dB will increase the noise by 1 dB.
The preceding discussion of stability accounts for the
transistor internal feedback only. In order to realize the
stable gain capabilities of the transistor as outlined, the
external circuit feedback should be reduced to a minimum.
1

Therefore, it is necessary to shield the input from the output circuit, to provide a low- impedance path to ground
for the common transistor lead, and to assure adequate
a.e. decoupling of the power supply. If sockets are used,
they must have low feedback capacitances and permit
electrical contact to be made very close to the transistor
header.
At high frequencies, lead length becomes quite important
and it is necessary to determine the maximum lengths that
can be tolerated at a particular frequency with lumped
constants. Generally, the lead lengths should be short in
comparison to a wavelength. A rough rule of thumb is to
limit the lengths to less than 002 wavelength. In the higher v.h.f. and u.h.f. ranges, this restriction becomes impractical and the inductance of the lead must be taken into
account.

ELECTRONICS WORLD

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The author, inventor of annular semiconductor devices, has been active
in semiconductor development since college. As manager of Motorola
Device Development, he was both an active participant and section manager. He received his BS and MS degrees in electrical engineering from

MIT and is presently manager of the company's Thyristor Operations.

Diffused Transistors
By JACK HAENICHEN /Manager, Thyristor Operations
Motorola Inc., Semiconductor Products Division

Annular, mesa, epitaxial, interdigitated -what do all
these terms mean? When should a diffused transistor
be selected? The answers are supplied in the article.
in which impurities are added to a crystal
of germanium or silicon not only determines what the
transistor is called but also its electrical and thermal
behavior. In the "grown" process, the required junctions are
formed while the crystal is being grown. As the crystal is
being pulled or grown from a vessel containing molten silicon
or germanium, the impuritiy content of the melt is changed
with time and contiguous n- and p -type regions are formed.
Because of its low yield. high cost, and other limitations. the
grown transistor has been supplanted by the superior diffused device.
When certain metals are alloyed with semiconductors in
the alloy process, a small regrowth region is formed in the

THE manner

semiconductor near the interface of the two materials. If
the metal being alloyed contains p- or tt -type impurities. the
regrowth region will retain a certain amount of these impurities. making it either a p- or an n -type, respectively.
Alloy transistors are being gradually replaced by diffused
transistors but still find use in high -power applications.
In epitaxial growth. silicon deposits itself and grows upon
the original .substrate, forming a mechanical extension of it.
If a small quantity of p- or n -type dopant is added, the
latter will grow p- or n -type, respectively. The epitaxial
transistor offers a high B1'c,,tu with good frequency response and high switching speeds.
In the diffusion process, while the semiconductor wafers
are hot, a source containing the desired impurities is presented to their surfaces and the impurities distribute themselves within the crystal. The final impurity concentration
is maximum at the surface and falls off exponentially in the
wafer. Because of this exponential impurity profile, a built -in
field is established in the base. This aids in transporting
charges from the emitter to collector and. as a result, the
frequency response of the transistor is improved. Today base
widths have shrunk from several mils to less than one micron,
making the electric field provided by a diffused base region
of little importance. However, the great degree of control
afforded by diffusion, as opposed to other techniques, makes
this process most attractive and economical. In addition,
reliability of the ciffused devices is usually claimed to be
greater than those made by other processes.

Diffused Transistor Structures
In the mesa diffused transistor (Fig. 1A) the emitter
,

regions are formed selectively either by an alloy or a masked
diffusion technique. A series of "mesas" are etched away tt
interrupt the continuous base region. This restricts the size
of the base and reduces the base- collector capacitance. It
July, 1967

the emitter -base and collector -base junctions are brought
to the surface, a planar diffused transistor results (Fig. 1BI
The silicon dioxide coating used for masking is often left
on the wafer or a new coating is applied after all diffusions
are completed. A permanent coating inhibits foreign material from reaching the junctions and other critical regions
near the surface where it might interact with the normal
action of the transistor. Such coatings have been referred
to as passivating coatings.
It was found that such a coating could aggravate. rather
than help, the situation because of impurities within the
coating itself. One of the most serious effects is channeling.
wherein the presence of the oxide coating actually disrupts
the charge distribution near the surface of the wafer in such
a way as to cause an inversion of conductivity type. For
example. in an 15- p-11 transistor where the collector isnoruTally ce -type, a p -type inversion layer or channel forms under
the coating. Such a channel constitutes an extension of the
base region and not only increases the effective size of this
region. but also causes erratic behavior of the reverse current.
In the annular transistor these channels are interrupted and
terminated by a positive annular band, as illustrated in Fig.
.

1C.

Since the basic starting material in the structures just described is the collector. it is most common to find the collector
connected to the case of diffused transistors.
In order to obtain maximum current rating with minimum
device capacitance, the structures shown in Fig. -2 were developed. Fig. '2 (left) shows a star transistor where the
emitter region consists of four tapered "fingers" radiating
from a center point which serves as an emitter bonding
island. Tapering of the fingers is consistent with the fact
Fig. 1. Three main types of diffused transistor structures.
EMITTER -BASE

_
P
(COLLEÇTOR)

PASSIVATING
COATING

EMITTER -BASE
JUNCTION

(EMITTER)

JUNCTION

ETCHED
MESA

BASE-

COLLECTOR JUNCTION

PLANAR

MESA

(B)

(A)
EMITTER -BASE

PASSIVATING
COATING

BASE

-N -TYPE CHANNEL

JUNCTIONN

j
DIFFUSED CHANNEL INTERRUPTING REGION

COLLECTOR
JUNCTION

ANNULAR

IC)

NOTE

CROSS-HATCHED
AREAS ARE
METAL CONTACTS

iluut current is continually leaving the finger toward its end.
In Fig. .1 (center) one sees an interdigitated geometry where
a large number of slender fingers are interconnected to form
multiple interlaced base and emitter regions, tightly packed
into a small area. Such structures provide a high emitter
perimeter -to -area ratio which has large current- carrying capability and low capacitance. An extended version of such
structures is used in many silicon power transistors (Fig.
?, right) .This all- diffused device can carry 50 amps of current in a. chip measuring 1?0 x 150 toils.
Materials: Only germanium and silicon are used in production units, despite the better theoretical suitability of
such materials as gallium arsenide (GaAs) It has been
found that III -IV compounds (e.g.. GaAs) possess such untenable chemical and metallurgical properties that ordinary
processes of diffusion, etc. become extremely difficult for
.

transistors.

Silicon is dominant in most of the new designs because of
its processing flexibility and high temperature capability.
Development of new germanium devices continues to be
important, especially in the microwave field and in certain
parts of the power- transistor field.
Cost: Fig. compares pricing trends of transistors and
tubes over the past 1? years. On a function- for -function
basis, transistors today are less expensive to fabricate than
are vacuum tubes.
13

Selecting Transistors
When a device is designed for optimum performance in
one or more parameters, compromises are often required in
the other parameters. Circuit. designers should be aware of
these interactions so that certain parameters are not over specified to the detriment of the others.
Breakdown voltages and junction capacitances: The
breakdown voltage of a diffused junction can be twice that
of an alloy junction. All things being equal, silicon junctions
provide higher voltage breakdown than germanium junctions. The circuit designer should not specify much higher
breakdown voltage ratings than required because lie might

have to pay for this voltage safety margin with a degradation in other key parameters. In alloy types, these trade -offs
are less severe.
Further, devices designed for extremely high -voltage
breakdown are likely to have more surface problems than
lower- voltage units. The depletion region at high voltage
is wide and the electric field associated with high- reverse
bias on such a junction will fringe into a volume outside the
chip, where possible interaction with its environment can
occur.
For low junction capacitance, a high collector resistivity
is used and the junction is kept small. A transistor having
a low collector capacitance, C l,, generally has a high BV elm;
conversely, a high C l, implies a low BVrrso- The circuit
designer should be cautioned about transistors with very
small values of emitter and collector capacitances since they
may oscillate spuriously in certain low-frequency circuits.
Current gain, ß: The behavior of /3 with collector current
for a typical diffused transistor is shown in Fig. 4. The
curves represent the performance of two silicon annular
transistors which are identical in all respects except for
breakdown voltage, Bl'c,o. It should be noted that in the
high -breakdown transistors, ß peaks at a lower current and
falls off much more rapidly with current than in the low breakdown case. This effect is often referred to as a forward
a.g.e. characteristic, because the gain decreases with increasing current.
Not shown are curves of gain-bandwidth product, IT, vs
collector current since they are similar to those of ß.
In general, diffused transistors have extremely low values
of inverse current gain (the current gain of the transistor
when the emitter and collector leads are interchanged in a
circuit) because the collector is more lightly doped than the
base. Typically, inverse /3 is less than utility. Alloy transistors
generally have a high reverse beta.
Saturation voltage, Vc.c,(s5T): This is usually specified at
some current and under a "forced
condition. Its value
is related to the forward and reverse current gains and the
series resistances in the collector and emitter. In general,

Table 1. Selection guide for popular germanium and silicon diffused transistors for various currents and voltages.

OPTIMUM COLLECTOR CURRENT RANGE
BV,

min
d.c.
19

10 ,A-10 mA d.c.
p-n-p
n-p-n

2N4411 2N708
t M M5000 2N3493

10-100 mA d.c.
p-n-p
n-p-n

tAF239
2N499

í2N559

2N869A

t2N960 -967
í2N968 -974
í2N700
í2N2415
í2N3127
í2N3279
í2N3283
í2N3783
í2N3784

,:.2N4125

2N916

40
59
60

2N915

2N3251
*2N3905
*2N3906

100-400 mA d.c.
p-n-p

2N2369
'`2N4264

t2N1142
í2N1195
í2N2929

2N3227

tMM380
2N1991

°`2N4265

2N1132

í2N2273
í2N2955
í2N3323
*2N3903 í2N502
*2N3904
2N2934-07
:2N4409 '°2N4402

`2N4403
2N2904A -07A

2N3251Á

n-p-n

400-800 mA d.c. 800-3000 mA d.c.
p-n-p

n-p-n

d-u-d

n-p-n

í2N1561
í2N1692

2N697

í2N1204
í2N1495
í2N2381

2N2218 -19

2N3252

2N2218A-2N3468
19A

2N3444 2N3719 2N3507

*2N4400
u2N4401

2N3720

79
80

2N3496

*2N4410

2N3499

119
120
if

2N3637
2N3743

2N3742

2N3501

Up
"i

Germanium devices:

Silicon plastic, all others are silicon metal

ELECTRONICS WORLD

www.americanradiohistory.com

Fig. 2. Photomicrographs of transistor geometries. (Left) star, (center) interdigitated and (right) power.

at high current, such as found in power applications, alloy
transistors have a lower value of this parameter than diffused
transistors because the collector and emitter series resistances of an alloy device are negligible. Further, germanium
transistors generally have an edge over silicon in this particular parameter and n -p -n's (Ge or Si) are superior to
p- n -p's.

Voltage VrE (sAT) is important with respect to power dissipation and loss of useful linear operating range in the transistor. Diffused epitaxial transistors provide lower VCE(SAT)
than non -epitaxial versions.
Base resistance, r,'. This is a distributed parameter, and
since the base impurity concentration is not uniform (exponential) is a diffused transistor, calculating r,,' is extremely difficult. For this reason, it is normally determined by a
high -frequency measurement.
Low r1,' designs have a low noise figure since a large portion of r.f. noise in diffused transistors is generated in the
base resistance. However, a low rb' generally means greater
emitter capacitance.
Input inr peda ce, 1ct,.: Input impedance decreases with increasing emitter current. A typical value at an emitter current of 1 mA is 1000 ohms, in contrast to an FET which
has an input impedance in the megohm range. Clearly,
where high input impedance is required, an FET should be
selected.

FET and UJT, will be available in plastic packages for
various applications.
passivated germanium transistors might become important since government- and industry- sponsored research continues in this area. In addition, considerable research is
under way with germanium as u.h.f. power sources. In this
work, diffused semiconductor chips are being incorporated
in strip -line and coaxial packages.
Compound semiconductors continue to frustrate the in$100.00
Si

10.00
Gel

TUBE-

1.00

304
10

1954

Fig. 3. Selling price of tubes and transistors over the years.
1.0

Replacing non- diffused transistors: In most instances direct replacement of a non -diffused transistor (e.g., alloy)
by a diffused type will not work well without circuit changes.
Saturation voltage, current gain versus current, etc. are quite
different than in non -diffused types. In general, the family
of diffused transistors is a much higher frequency breed of
device. Values of f. of 5011 \1Hz are common and amplifier
circuits with poor layout will often oscillate when a high frequency diffused transistor is used in place of an alloy or

LOW BREAKDOWN

grown device.

HIGH BREAKDOWN

Nevertheless, there are times when such changes can be
made, especially if some circuit modifications are possible.
Often a diffused device will be available in a plastic package
at considerably- lower cost than an older type. Also. silicon
devices can often be used to replace germanium, resulting
in improved high-temperature performance. Such replace ments must take into account silicon's higher saturation
resistance. With the passage of time, diffused types vVill be
more readily available as suppliers phase out production
of non -diffused transistors.
Device packaging: Diffused transistors come in a variety
of packages, including the TO -5, 18, 46, 51, it, and the
TO -9P?, a molded plastic package. Today's plastic- encapsulated passivated silicon transistor represents the minimum cost transistor configuration which the industry has been
seeking.
Table 1 is a selection guide for popular germanium and
silicon diffused transistors in terms of current and voltage
ratings.
Of the presently available types of diffused transistors,
it is likely that the passivated silicon device in a plastic
package will continue to be produced for the longest time.
Such transistors, as well as specialty devices including the

o
.001

.01

1.0

100

1000

10,000

COLLECTOR CURRENT, MILLIAMPERES

Fig.

4. Beta vs collector current for diffused transistors.

1000

Fig. 5. The r.f. power transistor trends. In just a

100

few years it is expected
that substantial increases
in output power and higher
operating frequencies will

readily obtainable.

July, 1967

1.0

0.1

100
1000
FREQUENCY, MHz.

10,000

www.americanradiohistory.com

dustry. Diffused transistors have been fabricated in gallium
arsenide and other materials, but their performance has
been disappointing since it has been well below theoretically
predicted values. The possibility of a breakthrough in this
area still exists, however, and work continues.
Extension of existing diffused techniques will lead to
devices capable of many watts output at hundreds of megahertz (Fig. 5) Low- frequency silicon power transistors capable of handling perhaps 100 amperes will be developed. but
the author feels that the very- high -current, high -voltage
.

field will continue to be dominated by thyristors. Photolithographic techniques will continue to improve and allow
even smaller devices. Today's `2N3493 which operates at
10 ttA will be complemented by devices operating at currents
orders of magnitude lower.
Devices such as the FET. UJT, and microwave bipolar
diffused transistors are continuing to acquire a share of the
market now enjoyed by other active devices. In many instances, UJT's or FET's can do a job easier, cheaper, and

better than conventional transistors.

ALLOY TRANSISTORS
HE alloy transistor, one of the first produced bipolar
junction transistors. has been superseded by diffused junction devices such as the mesa, planar. and epitaxial
types for the majority of applications. The diffusion process
yields low -cost high -quality transistors with excellent electrical characteristics and reliability. Today, alloy devices are
used primarily for replacement or when they can be purchased cheaper than comparable diffused transistors. In general, a fairly constant beta is collector current and a low
collector sat oration voltage are characteristics of alloy devices. Table 1 is a random sampling of alloy transistors and
some of their characteristics.
It should be pointed out that many germanium power
transistors are fabricated by the alloy process with either
homogeneous or graded bases. (For further details on this
subject, see "Power Transistors" in this special section.)
Most alloy transistors are p -n -p germanium and this will
be assumed in the following discussion. For the basic alloy
process, two small "clots" of a p -type impurity like indium
are placed on opposite sides of a thin wafer of n -type material (germanium) which serves as the base (Fig. 1) After
sufficient heating, the two dots alloy with the n -type wafer
to form the regions for the emitter and collector junctions.
and a p -n -p transistor is formed. The base connection in this
structure is made to the original semiconductor Nvafer. Because the collector has to dissipate greater power than the
emitter, and the current from the emitter diverges as it flows
toward the collector, the collector "dot" is larger than the
emitter "clot."
In the drift transistor, a modification of the alloy junction
device, the concentration of n. -type impurity in the base is
non- uniform, i.e., graded. Advantages of the drift device
over the basic alloy transistor are improved transit time,
higher collector breakdown voltage, reduced collector junction capacitance, and greater power gain. These advantages
lead to a substantial extension of the frequency performance.
Another important variation of the alloy transistor is the

micro -alloy diffused transistor (\IADT) In this process,
pits are electrochemically etched away from the n -type
wafer until a very thin effective base width is achieved. The
p -type impurities are then plated on each side of the wafer
and a p -n -p transistor is produced. These transistors have
very fast switching speeds and low saturation voltages,
making then ideal for direct -coupled transistor logic.
The future for new types of alloy transistors is dim since
most current research is directed toward the improvement
of the diffused and field -effect transistors.
Among the advantages of these latter two transistor types
are: the use of a relatively light impurity concentration in
the collector region of a diffused transistor resulting in high
collector breakdown voltages and low collector junction
capacitance: and in the case of the field -effect transistor, its
very high input impedance.
These two types are also the basic ingredients of the integrated circuit and this type of semiconductor circuit is rapidly becoming more important in all areas of switching and
linear applications.
.

EMITTER

Table

1. A

Example

EMITTER DOT

BASE

WAFER

COLLECTOR DOT

COLLECTOR
Fig. 1. In an alloy transistor, two "dots" of impurity
element are placed on opposite sides of the base wafer.

random sampling of some alloy transistors, divided into areas of interest, and their characteristics.
PC

BVCSo

(mW)*

(V)

50
120

40
90

70
20

120
120

p -n -p Ge

20
90

n-p-n Ge
p-n-p Ge

150
150

25
25

150
100

p -n

-p Ge

150 W

p -n-p Ge

50 W

45
60

37
90

7.5 MHz

Type

h,t:

V(.1)

(kHz)*

AT)

(V)

too

(µsec)

torr
(µsec)

Package (TO

Small- signal audio
2N591
2N1310

p -n -p Ge
n -p -n Ge

700

1000

High frequency

2N1090
2N1397

n -p -n Ge

5 MHz

120

Switching
2N388
2N404A

0.2
0.1

0.5

1.4

0.36

0.57

Power

2N173
2N1905

36
3

"unless otherwise sated

ELECTRONICS WORLD

www.americanradiohistory.com

The author received his BSEE in 1956 and his
Masters in 1964 from Purdue. He has been with
Delco Radio since 1956 and has served in various engineering posts in a number of departments of the company. His most recent assignment is as Group Leader of germanium device
system design, a job he has held since 1965.

Power Transistors
By RONALD W. VAHLE
Delco Radio Div., General Motors Corp.

Practical guidelines are offered for selecting the right
transistor for a power application. Various tables and
graphs are provided to simplify the selection process.
POWER transistors are required where operation at
large signal swings and appreciable power levels (1
watt or more) is of prime concern. Applications, in
general, involve driving transducers, high -level power
switching, and linear amplifications. Due to the requirements of these applications, power transistors are normally utilized in ranges where small -signal concepts and
models cannot be effectively used. However, where low level amplification is desired, many of the small- signal concepts and models are valid if the base spreading resistance
and emitter resistance are accounted for. Some typical
values are 10 ohms for the former and 0.04 ohm for the
latter. For high -power applications, graphical solutions are
still required. With the advent of computerized design,
more complex power transistor models may be developed
which will replace the graphic approach.
A prime concern in power-transistor design is power handling capability. For this reason, power transistor elements are first mounted to a good thermal base (usually
copper) with provisions to transfer heat from this base to
the surrounding environment. To minimize hot spots within the transistor ,junction, uniform current flow is necessary.
This then dictates ;junction size, collector size. and base
width. These factors dictate performance with frequency
response dependent upon base width and collector size. Thus,
incompatibility exists between high power handling and
high -gain, high -frequency performance.
Both germanium and silicon power transistors are avail-

able. Most germanium transistors are made by the alloy
process with either a homogeneous or diffused base. Silicon
power transistors are of double- or triple -diffused construction with a few selected types having the diffused
emitter and collector separated by a homogeneous base.
The latter devices are limited to relatively low- frequency
power applications, whereas double- and triple- diffused
power transistors are available in a wide range of voltage,
current. and frequency ratings.
Table 1 lists representative germanium and silicon
power transistors and includes the high current, low voltage and low current, high voltage ends of the operating

spectrum.
For most applications, power transistors can be adequately defined by only a few of the many available parameters. Table '? lists the significant parameters in terms
of two general application areas for power transistors
amplification and switching. In establishing the transistor
parameters for a given application, breakdown voltage,
current gain, frequency response, and leakage must be

specified.

Breakdown voltage: When the transistor is biased at a
high current operating point, Vr;10 or VCE(sus) should be
specified as the maximum voltage. For the transistor operating in the "off" or nonconducting state, then VIES,
Vcr;o, Vc:ER. or VCEs ratings are satisfactory. These ratings, which are based on zero or extremely low collector
current, should never be used when the transistor is to

Table 1. A number of representative examples of popular power transistors and their operating ranges.
OPERATING RANGE
TRANSISTOR
CONSTRUCTION

Germanium,
homogeneous base
Germanium, high-current homogeneous base

Silicon,
homogeneous base
Silicon, high- frequency
diffused base

Vrr,n

Germanium,
diffused base

Pr,,:,.,

APPLICATION AREA

EXAMPLES

Vers

(25 °C)
7A

300 kHz

100 W

Audio amplifier,
solenoid driver

DTG -110
2N392 & 2N301

- --

50 A

200 kHz

150 W

Regulators and
converters

2N1523

- --

Amplifiers and
switching

2N3055

100 V

High- frequency
power amplifier

2N3925

- --

DTS -100

100 V

DTS -402

700 V

DTG -1106

100 V

15 A

60 V

500 kHz

85 W

18 V

100 MHz

2 W

60 V

6 MHz

100 W

Amplifier & switching

4 MHz

100 W

H.V.

MHz

100 W

Low -distortion, high frequency audio amp.

500 kHz

100 W

15 A

Silicon,
diffused base

3 A

325

25 A

60 V

25 A

120 V

switching &
flection

TV de-

Inductive high- current
switching

DTG -2400

2N1653 & 2N2834

300

July, 1967

www.americanradiohistory.com

POWER -

AMPLIFIER
PARAMETERS

SWITCHING CIRCUIT
PARAMETERS

PARAM-

HIGH -FREQ. AMP.
PARAMETERS

RELIABILITY
PARAMETERS

VCE(.,AT)

Vr:u

V,I

ViLg, or VCI:>

VEB(SAT)

I('B(,

PET

VCE(SUS)

t,,,

Power gain

toff

or VcE1

V1;11

Insignificant over normal

V,;B

VCE(SeS)

ICRO,ICER,ICES,

Or ICES
OR

Insignificant over normal

Decreases 2.0 mV
per °C increase

Doubles approximately 11° C temperature increase

Ge & Si

Not applicable

VCEO

Resistance positive at low Increases with incurrent then becomes nega- creasing temperature
tive with increasing current

VEO

HIGH- IMPEDANCE

VOLTMETER

VCE,

VC!°
CV

(A)

(B)

Fig. 1. (Al Breakdown voltage dependence on the amount of
collector current (B) Test circuit used to measure value of V11.

conduct any appreciable amount of collector current.
The collector voltage -current dependence for the various
breakdown conditions is shown in Fig. 1A. It is important
to note that whenever appreciable collector current flows,
the breakdown curve, irrespective of condition, approaches
the
curve.
In order to evaluate transistor voltage capabilities at
high current levels, the sustaining voltage (Vc.(;(,y( -s)) test
was developed. The transistor under test is subjected to a
specified peak current and voltage condition simultaneously. The maximum collector-emitter voltage the transistor
sees should never exceed l'('E(sr;s) when conducting large
collector currents.
Gain and frequency: In specifying hFE, the ratio of required collector -to -base current should be multiplied by
1.5. This ensures reliable operation even with possible
transistor aging and gain degradation.
High-frequency gain is a linear parameter and is used
in amplifier applications. Here the gain requirement,
normally specified in terms of fT, is determined by multiplying LIFE by the upper cut -off frequency. For example,
if an amplifier requires an h(,,E of 30 and the desired frequency response of the system is 10 kHz, then an fT =
300 kHz would be required without feedback.
Leakage: Transistor leakage is normally considered with
respect to thermal stability and consequently must be
evaluated in tennis of the maximum temperature and voltage the transistor will see. Since leakage parameters are
closely related to the circuit design, it is not practical to
include all possible contingencies of temperature and voltage on a data sheet.
For germanium, Icaa at room temperature (25° C) is
provided on the data sheet and, generally, the lower the
specified 1(:110 rating, the lower the transistor leakage.
(For silicon, /('BO can be ignored up to about 150° C.)
Since in many circuits the transistor is not turned off in
an Icua mode, the designer can often reduce costs by
evaluating available transistors in ternis of actual leakage,
such as IcER or 1cEs, instead of Ic.EO.

Reliability and Parameter Variation
The preceding parameters will, in most cases, adequately define the transistor requirements for a given power

Decreases 2.2 mV
per °C increase

(2 V)

VCE(SAT1

Table 2. Important parameters for various power applications.

CHANGE WITH TEMP.

range

VEB

VCE°

range

NA.]r.

VaBO

MATERIAL CHANGE WITH CURRENT

ETER

Ge & Si

Increases with increasing temperature

See Fig. 2

See Fig. 3

Table 3. Parameter variations with current and temperature.

application. However. two other specifications-floating
potential (V11) and pulse energy test (PET) -should be
added for reasons of device reliability.
One of the easiest of all power transistor parameters to
measure. and one of the most important, is Fri. This test
(Fig. 1B) consists of measuring the potential developed
across the emitter-base junction (VfO at a specified collector -base voltage (e.g., V,,1;0). Mechanical defects or
major manufacturing errors will show up as a significant
emitter -base voltage. If this potential exceeds 0.5 volt, the
unit should be considered a reliability hazard. Life test
data has shown that units with a high I'f( fail five times
faster than those with low Vfr potentials.
A second reliability test. which subjects the transistor
to a power pulse for a specified length of time, is the pulse
energy test. The ability of a transistor to withstand this
power pulse is a measure of the transistor's durability. Because of the destructive nature of the test, its primary importance is to establish and insure product capability. It is
well suited to comparing the energy capabilities of various
transistor types intended for the same application. Since
it is potentially destructive, PET is not suitable for 100%
production testing, but this (loes not limit its usefulness as
a Quality Assurance Test.
Transistor parameters appear on most data sheets at a
specific operating point and temperature. Some of the
parameter variations encountered are inherent in the bulk
material used for the transistor and others depend strictly
upon device design. A summary of these variations with
current and temperature are provided in Table 3 and
Figs. 2 and 3.

Selecting and Specifying the Transistor
In selecting a transistor for a given application, the
important criteria are performance, reliability, and cost.
Obviously, the highest reliability transistor is unsatisfactory if it will not perform in its intended application.
Conversely, a very low -cost device may, in reality, be
quite expensive if its reliability or performance is unsatisfactory. Performance criteria should be established first,
closely followed by reliability standards. The most economical one should be selected from transistors meeting these
requirements.
Table 4 lists some specific application areas and expressions for computing required transistor characteristics.
For maximum reliability, a VCE(sus) (and V11 for germanium transistors) should appear on every specification
for the maximum voltage and current expected under
worst-case conditions. The use of Table 4 in selecting a
transistor is demonstrated in the following example.
Example: Consider a .'25 -watt, class -AB amplifier, with
a transformerless output and 8-ohm load, using two power
supplies of °72 volts each. Determine the transistor specification.

ELECTRONICS

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WORLD

700

180
HOMOGENEOUS -BASE GERMANIUM
160

600

140

.25°C

120

500

DIFFUSED -BASE GERMANIUM
100

\
1400 \

\LL

\°

300
20

\\J

DIFFUSED-BASE SILICON
O

Fig. 2. Typical

Ic - AMPS
variation with different collector currents.

26
HOMOGENEOUS SILICON

DIFFUSED GERMANIUM

Iç=1A

/ / / / / 30/ / / /'i
/
40 45

(DIFFUSED -BASE GERMANIUM)

HOMOGENEOUS GERMANIUM

IC -AMPS
c- 8A(DIFFUSEO -BASE GERMANIUM)

Fig. 4. Voltage and current capabilities of power transistors.

40-

polarities are optimum for their respective materials and lend themselves to the most reliable
units at the lowest cost.
is desirable. These

ICIA

(DIFFUSED -BASE SILICON)

30
20

Thermal Considerations

=3A (DIFFUSED -BASE SILICON)

Io
0

20
TC

Fig. 3. Typical hEU

-°C

variation with different temperatures.

1. From Table 4. the maximum voltage for the transis51 volts;
tor in the "off" condition is 2.3 V,.,. = 2.3 X ?
this corresponds to VeE Further, assume the "off" current will not exceed 25 mA.
2. The maximum-voltage, maximum- current condition
occurs under shorted load conditions and the voltage is
equal to V1.,.; consequently, specify VcE( sus ) _ 22 volts.
3. Normal peak operating current, from Table 4, is
_ 22/8 3 A. The base drive provided to the
amplifier is 100 mA peak; therefore an IiFE of 30 at 3
amperes is required. An kF,; = 1.5 X 30 = 45 at 3 A
should be specified. Assume l'c.F = 2 volts at the peak
current.
4. Since 15 -kHz operation is desired, with a feedback
factor of .707 an f .. of 30 X 15 X .707 or 318 kHz is needed.
5. Since VLF_t = 31 volts, a T71, = 0.5 volt is specified
at 51 volts.
6. Pulse energy requirements, under shorted load at 100
Hz, have been determined to be 4 amperes at 18 volts for
10 milliseconds. Therefore, PET = 4 X 18 X 10 X 10-3 =
720 millijoules is specified.
The specifications for the output transistor would be as
.

follows:
hFE ©
fT

le =

3 A, VcE

VcECSUS) @ 3 A

PET

2 V

@Ic= 4A,VUF =18V
=51V

Vfl @VC15
i (E.c @ 25 mA

45 min.
450 kHz
22 V min.
720 m
0.5 Vmax.
51 V min.

Transistor construction and polarities: The operating
capabilities of germanium and silicon devices are shown in
Fig. 4 for ambient temperatures below 100° C. For ambient temperatures greater than 100° C, only silicon transistors should be used.
Choice of transistor polarities depends on the basic transistor material. When silicon is chosen, an n -p -n polarity
should generally be used; for germanium, a p -n-p polarity

The d.c. derating curves, as supplied on most data
sheets, are indicative of transistor junction-to -case thermal
resistance and, for the most part, do not represent the
true limitations of the transistor described. In addition to
the junction -to -case thermal resistance, heat -sink thermal
resistance, mounting interface thermal resistances. and safe
operating area parameters must be considered when determining true maximum power dissipation for a given transistor.

Most heat sinks are specified with a still -air thermal resistance and decreasing thermal resistance with increasing
air flow.
Interface thermal resistance, that is, the effective heat
loss between the mounting base of the transistor and the
heat sink, must be accounted for. For a TO -3 package,
this value is usually 0.25 °C /W. and drops to 0.1 °C /W
with the addition of silicone oil to reduce the effect of surface irregularities. If transistor isolation from the heat
sink is required, then the use of a mica washer insulator
will increase the interface thermal resistance to 0.5 °C /W
For maximum heat flow, the heat sink should be isolated
from the circuit rather than the transistor isolated from
the heat sink.
Consider a TO -3 package with a thermal resistance of
0.8 °C /\V and 20 watts power cllissipation mounted on a
Delco 727072.5 heat sink. With silicone oil the thermal resistance of the assembly would be 3.2 °C /W (0.8 °C /W
junction -to -case + 0.1 °C /W case -to -heat sink + 2.3 °C /W
heat sink -to -air) In order to keep the transistor junction
below 110 °C with an ambient of 25 °C, the maximum
power is 26.5 watts (the temperature differential is 110 -25
= 85 °C; 85 °C /3.2 °C /W = 26.5 W). This figure reduces
to 10.9 watts with an ambient of 75 °C. If a mica insulator
is used in place of silicone oil, then the allowable power
dissipation would be reduced to 23.6 and 9.7 watts, respectively.
These power ratings, based on a maximum allowable
junction temperature and thermal resistance, cannot be
used for a specification but only as an approximate guide.
To determine the actual power rating specification, it is
necessary to make a careful analysis of the safe (maximum reliability) operating area. In addition, further de.

July, 1967

www.americanradiohistory.com

VCEX

APPLICATION

Amplifier-class

2 Voo

transformer coupled

Amplifier -class -B
transformeress P led

Voo

Amplifier-class-AB

Amplifier-class -B
transformerless
(single power supply)
Inverter (up to

5 kHz)

Vo02

2 RL'

Vc°

y,.
1.15

2 RL

V,.,.2

7r` RL'

'Co"

2 RL

fr
30 times max.
required frequency
response.

- --

30 times max.

y,r2
2 RL'

V, °2

V°

VCEO

VcEot -s)

1.15 V,,

required frequency
response.

30 times max.

1.15

V,,

required frequency

res P onse.

V,,2

1.15 V,ß

47r2

times max.
required frequency
response.

5 P.

Inverter (5 kHz -10 kHz)

V ° °'

°.
2.3

DEVICE

DISSIPATION

2 RL'

2.3 V,,

(2 power supplies)

POWER
OUT

2.3 V°°

RL'

transformerless

VCES

5.7

V-

5 P,,

5.7 V

4 V,°

200 kHz

400 kHz

where: RL' = reflected impedance seen by the output transistor; Rr. = load impedance; V,, = collector supply voltage; P° = output power.
Table 4. Specific application areas for power transistors and expressions for computing required characteristics.
A

ill111©i11\
B

(A)

(B)

Tc: 25 °C
4!

Fig. 5. (A) Uniform and (B) non -uniform current flow in power transistor. Latter condition may lead to second breakdown.

rating

is required for higher ambient temperatures and
different emitter-bias conditions.
Safe operating area: Consider the transistor structure
shown in Fig. 5. At low voltages (about 0.1 l',,EO) and
moderate currents (0.5 IC(rnar)) , uniform current flow
exists between emitter and collector as shown in Fig. 5A.
When either the voltage or current exceeds these figures,
current flow will tend to localize, as shown in Fig. 5B.
This can lead to the destruction of the transistor, a condition referred to as second breakdown.
Obviously, the temperature at point A of Fig. 5B will
be much greater than the corresponding point in Fig. 5A,
even though the temperature across the junction is identical. Because of this effect, the power capabilities of the
transistor decrease with increasing collector voltage.
To return to the previous example, where it was found
that '(i.5 watts could be dissipated with the heat sink
using silicone oil mounting, at voltages below 24 volts,
this figure is satisfactory. as shown by the safe operating
curve of Fig. 6. At 40 -volt operation, the maximum allowable power dissipation is reduced to t20 wal is (from Fig.
6) Although the average junction temperature is below
the maximum allowable 100 °C, some portion of the junction will he close to a critical temperature because of current concentration caused by high voltages.
Therefore, reliable performance depends on maintaining
transistor operation within the bounds not only of average
thermal resistance characteristics, but also within limitations dictated by a maximum reliability d.c. operating
area curve (Fig 6) . Total reliance only on thermal resistance calculations may lead to unreliable designs.
.

Future Outlook
Advances in power transistor technology will be in the
areas of new packaging concepts and higher voltage and
current ratings in both germanium and silicon devices.
Plastic -encapsulated transistors are already on the market
but in the 10 -watt and under range. Higher power designs,
exceeding 50 watts, are expected to be available soon in
the plastic package.

2;
2C

40
VCE

100

-VOLTS

Fig. 6. Safe operating curve for a power transistor (DTG- 24001.

The primary advantage of this package is lower cost,
although significant secondary advantages of smaller size
and lower weight are not to be overlooked. Wider lead
spacing in the plastic package simplifies the introduction
of very- high -voltage (1000 volts) transistors. Disadvantages of this package are its higher thermal resistance and
lower storage temperature ratings compared to the standard TO -3 package. It is apparent that the advantages out weigh the disadvantages.
Voltage ratings of Ver:s = 700 volts and VcE(s,;s) = 500
volts are now available. The 1000 -volt VCEV and 700 volt
VLE(ers) ratings are in pilot production.
Higher current transistors will be available in both
germanium and silicon structures. However, high -gain,
high- current devices will continue to be germanium. Silicon
power transistors will be more readily available with current ratings of "25 -50 amperes. These devices, however,
will normally have lower voltage ratings.
Much research has been clone in the area of second
breakdown and although some success has been achieved,
no major breakthroughs are foreseen in the near future.
In the pricing of germanium power transistors, moderate
price reductions will continue as manufacturing improvements occur. Silicon power transistors will probably continue to show significant price reductions.
A

ELECTRONICS

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WORLD

The author received his BS(EE) from Southern Methodist in
1950 and took postgraduate work in solid -state physics at
the University of Illinois. He joined Siliconix as Manager of Applications in April 1962, shortly after the company was formed. Prior to his present association, he
spent 12 years at Texas Instruments where he was active
in the design and development of semiconductor production and test equipment, germanium transistors, IC's, silicon FET's, and silicon diodes. He holds several FET patents.

Field -Effect Transistors
By ARTHUR D. EVANS
Vice -President and Engineering Manager, Siliconix, Inc.

What to look for in using JFET's and MOSFET's is considered.
Temperature effects as well as reliability are also covered.
L THOUGH quite old in concept, the field -effect transistorr (FET) is fairly new in availability. Two
basic types on the market today are the junction
FET (JFET) and the metal -oxide semiconductor FET
(MOSFET) The latter is also referred to as the insulated gate FET (IGFET) Figs. 1 and . show sectional views of
these two devices, both of which may have either a p- or
n- channel. Parameter symbols and definitions are provided
in Table 1, while the important parameters to be considered
in selecting an FET are listed in Table 2.

Table 1. Important

FET's have entered the consumer product price range.
For example, FET's have been used in FM tuners for
more than a year. As with bipolar transistors, FET prices
cover a wide range. Units packaged in epoxy are available
at less than +i0 cents each in production quantities. High quality, military -grade. hermetically sealed units cost much
more. The average price of FET's sold in 1966 was about
$3.90, down from a 1965 average of $7.00.

BVc

BV1,0 and BV.,,,,

circuited
Breakdown voltage from drain to source
with V,;, = 0
Breakdown voltage from drain to source
with V,;,
O. Normally specified for depletion -type MOS when V,;, > V.
Gate -leakage current. This current is
gate -to- channel in junction FET's, gate -

or
BVusx

IGSS

Inca and Iseo

Ino,rr> and Is,urn

Vos

Vr or Vr,s,rn+F>
h)

V6
AIVcs,-VoS21
JT
or lyfs1

g4s

g,,, or

MEANING
Breakdown voltage from gate -to- channel
with gate junction reverse -biased
Similar to the above except that either
source (BV,;,,) or drain (BV0,:,,) is open -

or By,;,,s

Device Characteristics
The JFET is a normally "on" device, i.e.. a conducting
channel connects the source to the drain even in the absence
The channel will conduct
of a gate -to- source voltage, V
current in either direction, source -to -drain or drain -tosource, its conduction being a function of V". For the
n- channel FET, a negative gate voltage depletes the channel
of carriers and thus lowers channel conduction. A positive
gate voltage has a similar effect on the p-channel device.
The magnitude of voltage required to reduce the channel
conduction to zero is called the pinch -off voltage, Vi.. Beyond i'i,, the only ,I.,. drain or source current that flows is
the reverse saturation current of the drain -gate or source gate p -n- junctions Joao and L,vun, respectively)
If the gate is forward-biased with respect to the source,
the channel conductance, g,t,,, will increase (Fig. 3) However, beyond it few tenths of a volt, the gate -to- channel
current begins to rise exponentially, hence forward -gate bias
is usually avoided for the JFET. The JFET has top and
bottom gate.:. In most devices, these two gates are connected internally_ and function as a single gate. However,
the gates can be separated and provide independent control
of channel conduction (e.g., the 3N89 tetrode) .
A very important characteristic of the MOSFET is that
the top gate is insulated from the channel by an oxide dielectric. In contrast to the JFET, the top gate can therefore be forward -biased to enhance the channel as well as
reverse -biased to deplete it. The back gate or body is
brought out to a separate terminal or is connected to the
source. It is seldom used as a means of controlling channel
conduction.
The insulated top gate makes feasible the normally "off"

parameters and their meanings.

PARAMETER

FET

g,,,
g)02

rn,

g,a.g,s or Rly1.,1,R1y,d
gs..,g,,.. or Re{ySS1,Riy.s1
C,

-,C

C,.a,Cag,Cag.,Ce

Css

C,,0. and C,go

July, 1967

to -body in MOS
Leakage current from drain (I,,,;,,) or
source
Drain -to- source current when V,,0 = 0
Match in I,.,, for differential pairs
Drain current under specified conditions
Sometimes used for drain current under
zero temperature coefficient conditions
Drain or source current with channel current cut off. V,., >V,
Gate -to- source voltage under specified
conditions
Gate pinch -off or cut -off voltage
Gate threshold voltage
Gate -to -gate differential offset voltage in
matched FET pairs
Incremental I,Vcs,
Vc,_ drift over temperature range
Magnitude
of small -signal, common source, short -circuit forward transfer conductance (admittance, transconductance
or transadmittance)
Match in gr, for differential pairs
Dynamic drain -source (channel) conductance; r,,, = 1 /g,,
Static drain -source resistance
r,,, and r,,, when Vo, = 0 in junction
FET's and when gate biased "on" in MOS
Small -signal, common -source, short -circuit, input conductance
Small- signal, common -source, short-circuit output conductance
Small- signal, common -source, short-circuit input capacitance
Small- signal, common -source, short-circuit reverse transfer capacitance
Small- signal, common -source, short-circuit output capacitance. Approximately
equal to Cros
Small signal source -to-gate capacitance,
gate shorted to drain. Approximately
equal to C,... in symmetrical units
Small signal drain -to -gate (or source -togate) capacitance with source (or drain)
open. Approximately equal to Cros

www.americanradiohistory.com

Digital
Switch

Analog
Switch

VGS(th)

ID(OFF)

Low -Freq.

Low -Noise

Amplifier

Cdgs/Csg

VGS(OFF)

ton
Cree
C uss

2N3386
2N3970
M103

ton
and

1VGS1- V: <_]

Low d.c. drift
Single -Ended

gigs

IDSS

VGS(OFF)

gr.

Il01- If..'I

VGS

Cr..

IDSS

gr.

l,;

Cros

VGS(OFF)

gf fagf sz

2N4339
2N4340
2N3458

2N4868

U205

2N4340

U231
2N3921

and

i,.

Electrometer

Amplifier

0¡

IDz(ID ZERO TC)

0 VGSl- V4:s_I
gf, at Inz

or
n

Differential
Amplifier

g16

gr,

r,.s(Gn)

ras(on)

High-Freq.

g`'"

at IDZ
at IDZ

IUZ

Inss
VGS(Ors)

2N3970
2N3386

2N3823
2N4223
U183

2N3578

2N3631
2N4119Á

2N2843
2N4117

M 106

G116F

Table 2. Pertinent parameters for a number of impor ant

///

%77777-/.I

-0G2

G2
A)
GI
Q

/G2

(F
Fig.

IA) N- channel and (B) p- channel junction FET's.
G

FET

applications, along with some device examples.

(enhancement -mode) devices in Fig. 2. As indicated in
Fig. 4A, a forward gate bias is required to enhance a channel
from source-to-drain and turn these units "On ". For the
normally "On" MOSFET (depletion-mode type) of Fig. ?,
channel conductance 1s gate voltage characteristics are
similar to junction units. An important difference, however,
is that the channel can be further enhanced by a forward
bias 011 the gate, as shown in Fig. 4B. The input resistance
of the MOSFET gate is extremely high due to the good
insulating properties of the silicon -oxide dielectric. Values
in the range of 10' ohms are common (e.g.. the 4\3631).
Usually, the leakage of the device package is the limiting
factor.
The JFET gate has the characteristics of an a -p diode.
Normally, it is reverse -biased and gate input leakage cur rent I(;,ss, at -23 °C ranges from less than one picaamperc
(4N 4117A) to a few nanoanlperes, depending upon device
geometry and manufacture. As with junction diodes,
approximately doubles for each ]f) °C temperature rise.
The gate voltage of the JFET is limited in the reverse
direction by avalanche breakdown of the gate -to- source
and gate -to -drain diodes. For the MOSFET, the gate voltage limitation is the destructive breakdown of the oxide dielectric under the gate. This breakdown must be avoided,
otherwise permanent damage to the oxide results. Gate
protection can he included within the device in the form of
a breakdown tener) diode between the gate and body.
If the application requires very high input impedance, the
diode is not usually included. However, for most switching
applications it is provided.
Package types. The majority of FET's are mounted in
the common 3- or -lead TO -IS type transistor package.
for the gate. For
Most p- channel JFET's use terminal
li- channel .1FET's, terminal 3 is commonly used. The gate
may be electrically connected to the case or, if the unit is
isolate(], the case may be connected separately to pin 4.
When the gate is connected to the case- care must be taken
to insulate it from ground when mounting the device in a
circuit.
IIOSFET's usually require four active terminals because
of the body connection. _]lost available devices have the
case and body connected to a common pin. Typically, their
terminal connections follow neither of the junction FET
connections.
Temperature effects. Mobility of majority carriers in the
FET channel has a negative temperature coefficient. Therefore, except under certain bias conditions, drain current,
transconductance, and channel conductance have negative
temperature coefficients. If the JFET is biased for constant
drain current ID, the major temperature effect is on the gate
(

G2lBODY1

G2IBODY)
G

rin
i*
G2

(BODY)

°2

F-

ós
B1

Fig. 2. MOSFET types. Top to bottom: depletion, enhance mens, symbol for the (A) n-channel and (B) p- channel types.
ELECTRONICS

www.americanradiohistory.com

WORLD

leakage current I,;,,,,, which approximately doubles for each
10 °C increase in temperature. The room-temperature value
of gate current for Ioday's a- channel ,IFET is so low that
even at U25 °C it may .Lill he less than 50 X 10 -" Ain a
typical aunplifier circuit. For even lower iupltt leakage current at high temperatures, an n-cltamnel NIOSF1:T such as
the ?N3031 may he used.
FE'l' performance in general improves as temperature
decreases; operation is good below -i200°C. The low-temperature limit occur~ When an inadequate number of impurities in the channel arc ionized to provide carriers.
Sufficient carriers are available at -'150 °C for channel
conduction of about one half the room -temperature value.
Ilrliabilify. The mechanical structure and packaging of
FET devices are similar enough to the bipolar transistor
to stake their mechanical failure mechanisms comparable.
The parameters (yr.I;,ss,l' ;.,y
associated with the
buried part of the device, that is, away from the .surface
of the silicon oxide interface. are extremely stable with time.
Stability of surface-dependent parameters, like leakage current and breakdown voltage, is a function of device geometry and processing. An inverted surface which may result
in high leakage or low breakdown, cannot be seen by visual
inspection. It can, however, he detected by an analysis of
electrical measurements, and is thus subject to quality
control.
For the AIOSFET, good duality control is extremely inn portanL since, by design, its channel parameters ('r,t,.,gj.,.,
are dependent upon the existence of an inversion
layer. 'l'hc stability of these parameters depends on the
stability of the inversion layer. Under normal operating
conditions, i.e., less than 15 °C, 17 shifts in the q,;,, rs
characteristic are small. In most switching applications
where 17, ;,, may swing front (t Lo 30 volts, the shift is
negligible.
A special handling problem for AIOSFET's is the prevention of static charge build -up on an open gate lead. Because of the low leakage of the \IOS gate (less than 10-'
A /V) sufficient static charge may accumulate on the gate
aanid result in a voltage -induced breakdown of the gate oxide.
One common means of avoiding this problem is to build
into the device a breakdown diode between the gate and
the body, as mentioned earlier. For units without builtin protection. care should he taken to ensure that a short
circuit or leakage path exists from the gate to another
terminal until the unit is in a test socket or circuit. A
gate -to- channel voltage in excess of about 100 volts may
cause permanent damage to the device.
Some manufacturers solder the tips of the leads together
prior to shipping; other ship in a special container lined with
conductive foil which shorts the leads together. When handling the device. it is a good idea to provide a leakage path
from the gale lead to another lead by holding a finger
against both. If common good engineering. practices are observed, little hauiulling trouble will be experienced in working with these IOSFE'I"s.

and the traunsconductance yf, is fairly independent of
drain voltage. This maximizes the voltage amplification
factor. !less. /y,,.,.,.
At high frequencies, capacitance becomes important and
more complex equivalent circuits are required (Fig. GB)
As the operati ig frequency is increased, input conductance
is low

)

Making lite Selection
The output twit transfer characteristics of a typical
channel channel FET (?N 1310) are shown in Fig. 5.
Similarity to the characteristics of a pentode vacuum tube
is obvious auul suggests direct FE'l' substitution in many
tube circuits. Indeed. FI:'C performance is superior in many
applications ranging from low -drift etc. amplifiers. through
low -noise audio. video, and r.f. up to several hundred MHz.
low -frequency small- signal equivalent model for the
FEi' is given in Fig. 0.1. The parameter values ye., and ry,,,
are a function of the operating point, (point "(4 in Fig. 5.k) .
Typically, for amplifiers, a drain-to -gate voltage greater
than the value of pinch -off voltage is used to minimize the
value of the output: conductance. ry,,,.,.. 'l'his region of operation is to the right of the dotted line in Fig. 5A where y

vos

acs

Fig. 3. Dynamic conductance curves vs voltage for JFET's.

gds

ONr

ON
n

-CHANNEL

o
VOS

-CHANNEL

(th)

Vos

VOS

(thl
VOS

(A)

acs

VOS

tel

Hg. 4. Dynamic conductance curves vs voltage for MOSFET's
of the (A) enhancement mode and (B) depletion mode types.
ves °ov

3.0
2.5

2.0
A. 1.5
1.0

0.5

h:
/i

`. _
5

2.5

<
E

2.0

,.5

-I2V

-LSV
2.0V

-2.5v

MaillOn

3.0

-05V

20 25 30 35 40 45
VDS-VOLTS

1.0

0.5

V.
5 -2 -15
V.,-VOLTS
(B)

-3.5 -3 -2

(A)
Fig.

5. (A)

Output,

(B)

VDS=10V

transfer characteristics of typical

-1

-0 5

FET.

Fig. 6. Small- signal equivalent circuits for the field- effect
transistor operating at (Al low frequency, (B) high frequency.

u>-

vin

iss

(Al

CGgs

vin

Cgd

Cc
g fs

July, 1967

goss

gfs viN

goss
(B)

www.americanradiohistory.com

and output conductance g
increase, while transconductance gr,. decreases. The maximum available gain (MAG)
drops to unity when g;,,.,.g .,.y = gr'/4. The frequency at
which this occurs is the maximum frequency of oscillation
for the device.
An important characteristic of the FET in r.f. circuitry
is its almost perfect square -law transfer characteristic (Fig.
5B) This results in amplifier cross-modulation distortion
figures of at least one order of magnitude better than those
of bipolar transistor designs.
In a low -noise amplifier the equivalent input noise voltage
en and current
are most important. Since these are frequency dependent, care must be taken in comparing device
types to note the frequency at which these parameters are
specified. Some device types have a specified noise figure,
NF, for a given operating condition with a given generator
resistance. Usually a high value of generator resistance is
specified to make the device "look good ". If the value of
NF is 3 dB, then the specified value of generator resistance
is equal to the equivalent noise resistance of the FET.
For a differential amplifier, the incremental input drift
over a specified temperature range is probably the most
important parameter. An often overlooked parameter in
this application is the differential output conductance,
9o.,al ,yoxa . If y,,.,,, is large or not well matched, the commonmode rejection will be poor. If the input signal source resistance is high, then the differential gate leakage current
'assr lass_ is also important.
When the FET is used as a switch for analog signals,
the series switch resistance rd, and the drain leakage current
gi.,,

lurorr7 are probably the most important parameters. Gate -

drain and gate -source capacitances are important because
they determine how much of a "spike" is rejected into the
analog signal path in turning the switch "on and "off ".
Vi. or Vr;sr17i1 will determine how much gate drive voltage
is needed to control the switch.
FET's are less susceptible to damage by high -energy
radiation than bipolar transistors. Type 2N3631 MOSFET's
perform well even after exposure to fast neutron radiation
of 10'° nvt. Major effect is increase in gf.,,IUSS, and V.

Power FET's
Several companies have reported work on the development of power FET's that approach operation in the 1 GHz
region. One method uses a gate structure embedded below
the silicon surface. Electrons flow clown from the source contact at the surface, through a grid of gate elements, then
to the silicon substrate which is the drain. Called a "Gridistor", this device is reportedly being worked on by Dr.
Stanislaw Teszner of France and is expected to be capable
of 5 watts at 300 MHz.
A similar multi- channel FET has been reported by R.
Zuleeg of Hughes Aircraft Solid State Research Center. For
five devices operating parallel, 2 watts of power was obtained at 100 MHz with an efficiency of 66 %. A different
approach was explored by Mitchell of RCA. Using a MOS
tetrode made by integrating two triodes on a single chip,
a cascole circuit achieved 12 dB gain at 800 MHz. It will
not be too long until power FET's become available to compete with bipolar transistors in many areas of application.

THE UNIJUNCTION TRANSISTOR
EVEN though the unijunction transistor was developed in 1954, the
electronics industry is just beginning to utilize the potentialities of
this remarkable, single p-n junction semiconductor device.
The unijunction transistor finds application in many different areas;
including timing circuits, multivibrators, pulse generators, SCR firing
circuits, saw -tooth generators, time -relay circuits, ring counters, and
voltage -sensing circuits. Maximum frequency of oscillation is approximately 1 MHz and, although low in price, the unijunction has excellent
linearity, stability, and requires very simple circuits which are stable
over a wide range of temperature variations.
As will be shown, the output from a unijunction oscillator can be either
a positive- or negative -going pulse accurately occurring at the flyback
of a saw -tooth waveform, which can also be used as the output.
Fig. lA shows the symbol for a unijunction, while Fig. 1B shows a
cross -sectional view of a typical unit. The n -type silicon bar has an aluminum wire (emitter) alloyed to it to form the only junction within the
device. The two base contacts, one at each end of the silicon bar, are
ohmic contacts only and are not rectifying junctions.
The resistance between base 1 and base 2 will vary (with various types
of unijunctions) from 4500 to approximately 12,000 ohms. In conventional operation, base 2 is connected to a source of positive voltage while
base 1 is connected to the negative end (usually ground). The base bar
acts as a conventional resistance and has a voltage gradient within it
ranging from a maximum at base 2 to zero at base 1. As the emitter is
connected at some point above zero, some fraction of the voltage applied
between the two bases also appears between the emitter and base 1. This
fraction, or proportional part of the voltage between the bases, is the
most important parameter of the device and is called "intrinsic standoff ratio or 77.
As shown in Fig. 1C, RII, and RB, represent the ohmic resistance of
the silicon base bar, while diode Dl represents the p -n junction formed
by the alloying of the aluminum emitter wire and the silicon bar.
If an external voltage (VE) is applied to the anode of the diode, and if
this voltage is less positive than the voltage on the diode cathode as a
result of the voltage division of the silicon bar (77Vßß), then the diode
will be reverse biased and no current will flow through it. Voltage 77Vßß
is referred to as the peak, or firing, point.
However, when V,: rises above 7711ß, the emitter junction will then be
forward biased and current will flow through the diode to base 1. This
increase in current flow consists primarily of minority current carriers
injected into the silicon bar. As a result of this rise in current flow, the
effective resistance of RB, is decreased, allowing still more emitter current

to flow, further reducing the effective resistance of RBI, thus producing a
negative- resistance characteristic.
There is a different peak point for each value of VBB due to a different
proportional voltage being applied at the emitter -bar junction, thus
reverse biasing the junction diode at different levels of voltage.
In most practical cases, a capacitor (C) is connected between the
emitter and ground, and a resistor (R,) is connected between this capacitor and the positive voltage source. A resistor (R:,) is connected between the positive voltage source and base 2 with another resistor (R,)
between base 1 and ground. When power is applied, capacitor C starts
to charge exponentially via R. towards the positive level. When the voltage
across the capacitor reaches V,, (firing point), emitter current starts to
flow and the resultant negative resistance action causes a very rapid
discharge of the capacitor. The action then restarts to form an unbroken
saw -tooth train available at the emitter junction. At the trailing (capacitor discharge) edge of the saw- tooth, a sharp negative -going pulse will
appear across R:,, while a similar but positive -going pulse will appear
across R,. The frequency of oscillation can be approximated by: f = 1/

(RP.
Resistor R:, is used primarily as temperature compensation and usual
values lie between 200 and 600 ohms. Resistor R, is determined by
the circuit signal levels required for a desired pulse output.
Recently, G -E introduced its D5K unijunction transistor whose characteristics are like those of conventional types, except that the currents
and voltages applied to it are reversed. That is, the positive voltage is
applied to base 1, and the p -n junction formed by the emitter and bar
is reversed. The intrinsic stand -off ratio is .58 to .63, or ±3%. The
unit has a low base 1 to emitter voltage drop at high current, permitting
high output pulses with low base -to -base voltages.

Fig. 1. Symbol, construction, and equivalent circuit of device.
BASE 2

BASE 2

EMITTER
ALUMINUM

BASE 2

WIRE

r
P

BASE!

s
0

-N JUNCTION
N

[

¡I

RBI

'tYBB IB

-TYPE

SILICON BAR

BASE
BASE

(Ar

-T

EMITTER

(B)

(C)

ELECTRONICS WORLD

www.americanradiohistory.com

author is an engineer /physicist. During his training at the University of
Toronto he studied such unrelated subjects as x -rays and spectroscopy, numerical
analysis and ultrasonic propagation in liquid helium. He holds a BA Sc degree
in engineering physics and MA and PhD degrees in physics. Since joining General
Electric's Semiconductor Applications Engineering Section (a section he now heads),
his responsibilities have included digital and pulse applications of unijunction
transistors and silicon controlled switches as well as conventional transistors.
The

Small -Signal
Low -Frequency

Transistors

By RICHARD A. STASIOR /Manager, Applications Engineering
Semiconductor Products, Electronic Components Div., General Electric Co.

Transistor differences, parameter variations, and
reliability are considered. A checklist is given
to help select transistors for audio applications.
transistor amplifies higher frequency signals, a
point is reached where gain begins to decrease. At
frequencies below this point the transistor is said
to be operating in its low- frequency region. There are
several constructional factors which control the frequency
at which gain decreases; these include the transistor's base
width, its junction capacitances, and the built -in resistances which work with the capacitances to reduce gain.
The newer planar silicon transistors generally extend their
low- frequency range beyond 1 MHz. For the purposes of
this article, we will consider low frequencies as synonymous
with audio frequencies.
If a "large" signal is applied to the transistor, in effect
the signal will vary the operating point over a considerable
range causing significant changes in the transistor characteristics. By contrast, a small signal is one that hardly
changes the operating point so that the transistor's input,
output, and gain characteristics can be considered constant. It is important to note that this definition does not
depend on power output, but rather on the constancy or
linearity of the transistor parameters. Therefore, a class -B
audio output amplifier delivering 50 m \V is an example of
a large- signal application: a power transistor class -A stage
supplying the same power represents a small -signal application. Amplifier transistors rated at less than 1 -watt dissipation are generally classed as "small- signal" devices.
All transistors generate appreciable noise at very low
frequencies. As frequency is increased, the noise decreases
to a lower constant level: audio transistors are designed to
minimize this noise. Because of the low small- signal power
levels, small, low -cost transistor structures can be used. For
example, for coupling into microphones, or low- output tape
recording heads, audio transistors need to combine low noise
with high current gain at low collector current.
High -frequency transistors, on the other hand. sacrifice
high gain and low noise in order to achieve narrow base
widths and low ,junction capacitances. In power transistors,
the more important factors are the thermal characteristics
of the case and the voltage ratings.
Switching transistors are designed to be an effective
short- circuit when turned "on"; when "off ", the leakage
current must be low. Since the speed with which a transistor responds to an input is important, its design incorporates a narrow base width and a low collector capaciAa

tance. For rapid turn -off, gold is introduced into the base
of the transistor to neutralize the carriers stored there
during the "on" state. Gold reduces the transistor's gain
and increases its noise. making it less suitable for audio
applications.
Examples of high -performance audio transistors include
the 2N3391, 2N3394, ?N3415. °?N3103. and the 2N508
series. The 2N3391 is characterized by low noise; where
low noise is not mandatory, the 2N339- is a low-cost transistor with a narrow current -gain range that simplifies circuit design. The 2N3115 has good linearity at higher
currents, while the 2í;1.03 offers the same electrical performance as the 2N3415 but at higher dissipation due to
its integral heat sink. The 2N508A is a p -n -p alloy germanium transistor with broad applications in audio circuits.
Areas of application for small -signal low-frequency transistors include FM- stereo multiplex decoders, electronic
organ oscillators. electrocardiogram amplifiers. servo amplifiers, and other similar circuitry.
Fig. 1. Normalized h- parameters vs collector current for 2N3391.
10.0

r
-

NORMALIZED

PARAMETERS

'J,
f

IO v

IKHZ

---

hoe

25'C

0.4

0.2

0.1

PARAMETERS AT Ia
h,e
i20K OHMS

h0, =
hre =
hre :

06
.04

O.Ima

hre.

26 ,. MHOS

74 x10_3

--.-

420

.02

.0I
.01

.02

.04

July, 1967

06 080.1

0.2

0 4

0.6 0.8

2.0

4.0

6 0 8.0

10.0

www.americanradiohistory.com

.,a

h PARAMETERS VS TEMPERATURE

2
W

5
4

hr.

f'
>
2

1.'3

Sen A

25°C

IKMr

-10V

IcImA

1.5

f IKHz

/All

h1e

hn.

hre

hfe

ho,

ohms

hoe =26ít mhos
3
hre = 74 X 10
Ate =420

hoe

=120

h,e

hte

la1

hre

hie

¢
a

Ver - COLLECTOR
(

VOLTAGE

30 40 50

-40 -30 -20

-10

VOLTS

TEMPERATURE

40
IN

100

°C

(81

)

Fig. 2. Family of normalized h- parameter curves shown as a function of (A) collector voltage and (B) temperature.

Important Device Parameters
The most useful and practical parameters for audio frequency applications are the small -signal parameters h
and lot,,, and the upper -3 dB cut -off frequency, f p (see
Table 1). When "current gain" is meant, the term beta
(ß) is often used rather than ht,. (or hFE) , For an effective load impedance of 10,000 ohms or less, It;,.
input
impedance of the amplifier: ht,, _ current gain of the amplifier: and f _ the upper -3 db cut -off frequency for
the amplifier.
The h- parameters. with capital subscripts (hmE, hFE,
hRE, and 110E) refer to average or d.c. parameters and are
useful for biasing the transistor. For example, if Ic =
10 mA and in = 0.5 mA (as measured on a v,o.m.) , hFE _

10 /0..5

Table 1. Small- signal parameters (common-emitter) for audio.
Upper
1

ho.
hi,.
h0,.
h,.,,

Y11

Y°1
Y1_

Y22

20.

While the h- parameters are easier to measure at low
frequencies, the y- parameters of Table 1 are more convenient for mathematical analysis and are more readily
measured at high frequencies. It is for this reason that
transistors such as the 2N3854 are characterized at l00,
45, 10.7, 4.5, and 1 \IHz in y- parameters and at 1 kHz in
h- parameters.
It is noteworthy that the li- parameters are measured at
only one operating point and normalized curves are supplied to permit calculation at other operating points. For
any given transistor manufacturing process, all the transistors tend to vary in the same manner with operating
point, irrespective of the actual value of the parameter.
that is, a high beta unit will have its beta peak at the
same collector current as does a low beta unit. Similarly,
the percentage change of beta with temperature will also
he relatively independent of the actual beta. For operating
points other than the one at which the parameters were
measured, the measured value is multiplied by the factor
shown on the vertical scale. Some example; of normalized
curves are illustrated in Figs. 1 and 2.

ft,

The relationship between ht,. and hFE is illustrated by
the curves of Fig. 3. Either one may be greater, depending
on the operating point at which they are compared. The
graph also shows that hfe decreases at higher frequencies.
Since there is a reasonable correlation between lot,. and h,FE,
frequently only one is measured for specification purposes
and the other estimated. However, current gain applies
only to the point of measurement. and the gain may be
different if the intended operating point is far removed.
The curves of Fig. 1 indicate typical variations of h. parameters with collector current. For a 1000 to 1 range in collector current, hte varies by less than 4 to I: therefore, beta can
be considered a constant once an approximate operating
point is chosen. Parameter h; on the other hand, changes

-3

dB cut -off frequency where hf,, is 0.707 its value at

kHz

Forward current gain
Input impedance

with output a.c. short -circuited

Output admittance
Reverse voltage transfer ratio

with input a.c. open- circuited

Ratio of total transistor noise power delivered to a load to the
noise power delivered to the same load by the source

Input admittance
with output a.c. short-circuited
Forward current -voltage ratio
Reverse current -voltage ratio
with input a.c. short- circuited
Output admittance

501-

100

O Oi

Fig. 3. Variation of h,, and har:

with collector current.

approximately 2(I(1 times in the same current range. Since
h;,, is very nearly equal to the input impedance of the
transistor, we see that the input impedance is approximately I megohm at IO p.A of collector current and 3600
ohms at 10 n1A. While h,.,,, the feedback factor, varies
drastically, its absolute value is so low that it may be
ignored. The variation of h,,,. can also be neglected when,
as is generally the case. the output of a transistor is
coupled into the base of another transistor.
Typical variations in the h- parameters with I'f.E for
small -signal audio transistors are given in Fig. A. Parameters ho. and hf,, are fairly constant over a wide range of
collector voltages. The variations in h ,. and h,.. can usually be ignored.

Variations in h- parameters with temperature are indicated in Fig. 2B. The most important variation is in ht,.;
of lesser importance is h;,., (The upper cut-off frequency f
behaves approximately as parameter h;,,.) Changes in h,.,.
and lt,,,. with temperature can usually be disregarded.
Noise seen at the collector of an amplifying transistor
ELECTRONICS

www.americanradiohistory.com

WORLD

depends on the signal- source impedance as well as the collector current. Typical curves of constant noise figure
(\ F') as a function of collector current and source resistance are shown in Fig. 4. From the graph it can be seen
that the best noise figure is obtained for source impedances
between 3000 and 10,000 ohms at a collector current of
approximately 40 AA.

IOK
8K
6K
4

sistor is the circuit and environmental performance requirements. There are the obvious constraints imposed by
the available supply voltage, humidity, shock, and temperature environment that add to the electrical requirements of gain, low noise. and manufacturability. An experimenter buying one transistor need not concern himself
with the last factor. However, any equipment manufacturer must go beyond the obvious circuit requirements and
consider available safety margins on the voltage ratings
and package dissipation. the uniformity of device characteristics from shipment to shipment, the versatility of the
transistor for other potential applications, amount of available design data, and packaging.
It is well to understand the more important factors that
influence cost. Planar transistor technology, which permits
hatch fabrication of hundreds of transistors simultaneously, yields excellent low -cost small- signal transistors. Another factor affecting cost is the transistor case. A hermetically sealed can is significantly more expensive than a
plastic encapsulation. Assembling the planar transistor
pellet on the header and welding leads to it are also expensive. Cost is also influenced by electrical specifications.
Generally high -voltage and high -current -gain specifications
raise cost by leaving residue for the manufacturer after he
selects to specifications. In other cases, special tests involving nonstandard temperatures or noise figures are expensive
to perform.
Reliability depends on the ability of the transistor to
perform in its intended application. This requires that one
consider the reliability of the circuit as a whole rather
than that of the transistor itself. For example, germanium
and silicon transistors and FET's will, in general, all meet
the demands of the consumer market. Germanium is currently used in most foreign portable radios. It offers acceptable radio performance, even after the battery voltage
has dropped to half its initial value, with simpler circuitry
than silicon devices permit. On the other hand, silicon
transistors are used in domestic radios because years of
American research in silicon have frequently brought silicon
transistor prices below those of germanium. Car radios

4 5 6 7 8 9 db NOISE FIGURE

Nii
I

2Ksommignisi

Selection Guidelines
First of the many factors to consider in selecting a tran-

éi;

' "",.
n _,,1-11a,"\"

111111.1_

800
600

400

00
60

`aUSIVM
I!IY
_.

Goll

200

_1111,,.

1
11

CONTOURS OF CONSTANT NOISE FIGURE
Te

5 6

25°C

1111

60 80 100

200

400 600 8001000 2000

(pA)

Fig. 4. Noise figure vs source resistance, collector current

(2N3391).

utilize silicon transistors to cope with high temperature
ambients. The field -effect transistor is slowly making inroads, but its price and little if any improvement in electrical performance in most circuit functions has not made
it too attractive.
The major potential problem with plastic encapsulated
transistors is penetration by humidity. This need not be a
problem if appropriate quality -control measures are implemented. Current life tests indicate that properly encapsulated plastic transistors rival the stability of hermetically
sealed units.
A checklist for selecting low- frequency small- signal transistors is given in Table Z. This list will help avoid overlooking some important factors in making the selection.
Cost was not explicitly identified because all factors contain cost implications. The user must decide how much
value each factor has in his application. In addition, questions to ask the manufacturer or his representative if you
are designing a piece of equipment for production purposes
include the following:
1. Are you recommending my* choice of transistor for
new designs?

Table 2. Here is a useful checklist to be employed in selecting small-signal audio transistors.

conventional amplifier.

Voltage ratings

V).no should exceed maximum voltage the transistor will see. Vrmo is of no importance in

Current ratings

I,.,,,,,t,)

Dissipation

is very

Current gain

he,,

and hF,., should be large.

Noise figure

For very low source impedance, a type such as the 2N508A germanium allow
ohm source impedance, a type such as the 2N3390A is recommended.
For 1- megohm source impedance, the FET gives best performance.

Case or packaging

Note whether case is electrically isolated from transistor. Small plastic transistors are available.

Versatility

Specifications can be extensive enough to permit use in most low- frequency applications without undue cost penalty.

Data

Curves showing transistor performance allow extrapolation

Power-supply
voltage range

Operating point easier to stabilize with germanium than silicon transistors if power supply voltage varies significantly.

Temperature

Germanium difficult to use in ambients exceeding 70 °C; silicon may be used to 125 °C. Silicon transistors
have negligible leakage current and more h- parameters than germanium.

Shock

Plastic encapsulation provides most rugged construction.

generally no problem.
low for small -signal applications.

"p -n -p"

is excellent. For 2000

to 50,000 -

of specifications with greater confidence.

Humidity

Most detrimental ambient is 40 °C and 95% relative humidity. Plastic transistors satisfactory for practical application.

Electrical
transients

Transistors should be protected against lightning or power- switching- induced transients. FET's are most vulnerable to
damage.

July, 1967

www.americanradiohistory.com

For what market is this transistor intended?
Under what other numbers are transistors of this

2.
3.

same process sold?
I. What cost advantage is there in relaxing some noncritical specifications?
5. What would it cost to tighten up on a critical parameter?

What Lies Ahead?
With the increased use of computers, more tightly controlled processing, resulting in less variation between transistors and less residue and thus lower cost, will be possible. The computer should also permit faster and more
sophisticated testing for better assurance of electrical performance. For the circuit designer, computer -aided design
will allow more accurate compensation for transistor variability, lower safety factors on specifications. and higher
performance from each transistor stage.

With all the current effort being directed to the development of integrated circuits (analog and switching) , there
is little doubt but that discrete transistors will eventually
become obsolete for most uses. The important questions are:
when ?, in what applications ?. and by what kind of integrated circuit? In retrospect, we see that after 18 years of
transistor progress. some electronic functions are still handled best by tubes. Similarly. today, low -noise transistors,
high -resistance values, and coupling and bypass capacitors
are a problem for integrated- circuit techniques.
While integrated circuits are improving. so are transistors. Also, new higher performance devices are constantly
being introduced, such as the new Darlington amplifier.
which is really two transistors integrated into a transistorlike structure. So while integrated circuits will continue to
supplant discrete transistors in the simpler applications.
we can expect to have discrete transistors with us for a
number of years to come.
A

RESONANT -GATE TRANSISTOR
ALTHOUGH the introduction of the semiconductor permitted circuits to get physically smaller, there has
always been one function that has been difficult to miniaturize. That is the frequency selective network usually
consisting of inductance and capacitance. In an effort to
do away with LC combinations, particularly at audio frequencies where the values of these components would be
inordinately large. circuit designers have resorted to relatively complex semiconductor circuits that perform the
frequency selection process.
The experimental field- effect transistor shown in Fig. 1
represents a new generation of semiconductors in that it
is a combination of frequency selective device and amplifier. Like all field -effect devices. it also has the advantage
of a very high input impedance.
As shown in Fig. 1, the gate electrode is cantilevered
over the other electrodes. The cantilever can be made to
mechanically vibrate at its resonant frequency by the application of an a.c. electrostatic field applied to the input electrode.
One end of the gate electrode is fixed to the silicon substrate while the free end is positioned over the input
electrode. Both these electrodes are insulated from the
silicon substrate by a silicon oxide (glass) layer.
If an alternating voltage. of a frequency matching the
mechanical resonant frequency of the cantilever, is applied
to the input electrode. the cantilever will vibrate at its
resonant frequency. The resultant field between the cantilever and the channel affects the conductivity between the
source and drain electrodes. The output is taken from the
drain in a conventional manner.
The polarizing voltage applied to the stationary section
of the cantilever reduces the second harmonic output
Fig. 1. The fundamental frequency is a function of the
mechanical resonance of the cantilevered gate electrode.
OUTPUT

CANTILEVER
GATE

LOAD
RESISTOR

DRAIN

POLARIZING
VOLTAGE
SOURCE

INPUT

CHANNEL
SILICON
SUBSTRATE

which arises. since. without this voltage. the electrostatic
force between cantilever and input electrode is proportional
to the square of the input voltage.
Such a device, having a gold cantilever 0.0-1 -inch long,
has been made to resonate at 3 kHz with a bandwidth of
30 Hz and a "Q" of about 150. Some other experimental
devices have been produced with fundamental resonances
from 1 to 7 kHz, with "Q's" up to 41)0. The devices can
operate in the overtone mode, with the overtones not
being related to the fundamental. The first and second
overtones occur at 6.`21 and 17.55 times the fundamental
frequency. thus enabling operation up to the lower i.f.
frequencies.
Devices with resonant frequencies up to 1 \IHz are
feasible. and gains of up to dB have been reported.
The beam resonance theory has been tested for use in
IC's as demonstrated by !B1! not too long ago. Called a
resonistor, the device is essentially a cantilevered chip of
silicon measuring 0.0350 -inch long 0.0911 -inch wide. and
0.008 -inch thick. mounted on a substrate.
An excitation electrode is connected near the stationary
end of the silicon device. and a strain sensor (piezoresistor)
is mounted farther out along the cantilever.
When an input signal is applied to the excitation electrode. it supplies ]teat to the slender silicon clip setting
up strains which cause the silicon to vibrate at its mechanical resonant frequency. The unsupported end vibrates up
and down approximately 50- millionths of an inch.
The vibration causes the output strain sensor to change
its resistance proportional to the vibrating frequency.
When d.c. is applied across the piezoresistor, a.c. -like output voltage is produced. The basic resonant frequency
can be controlled by weighting the unsupported end of
the cantilever.
Although the bulk of the output signal occurs at the
cantilever resonant frequency. a smaller signal appears at
half the resonant frequency. Several resonistors operating
at different frequencies have been built.
Frequency selection by application of mechanical forces
applied to a semiconductor have also been carried out in the
audio field. Here the surface in the emitter region of a planar transistor is mechanically stressed by a stylus. The stress
changes the emitter -base clsu'acteristics, and hence changes
in the stress level create changes in the transistor parameters. If the stylus is mechanically connected to a diaphragm,
the transistor acts as a microphone.
Stressed transistors have also been used in multivibrator
A
circuits where stress level determines frequency.
13

ELECTRONICS WORLD

www.americanradiohistory.com

Fierro has been with Fairchild Semiconductor for
years. He is a Senior Electronics Technician
with an electronics degree from City College of San
Francisco. He is working on the characteristics of
transistors including those of switching transistors.
S.

41/2

Switching Transistors
By STEVE FIERRO
Fairchild Semiconductor

Important factors in choosing a transistor for computer
and high -level switching applications are considered. Also
included is a graphical method for predicting storage time.
comluctor material during the fabrication process. Gold
diffused into silicon or germanium has the effect of introducing recombination centers which reduce the lifetime
of minority carriers in the collector of the transistor. It is
these minority carriers which give rise to storage time.
Table 1 lists representative transistors designed for
switching applications while the important device parameters arc summarized in Table ?. Today. the diffused
planar epitaxial transistor type is preferred in most applications. Its reliability is high and the price, in the plastic
package, is duite low. The diffused transistor is available
in standard ITO -:i, 18, 39, 46, 5 '2, etc.) and in non -standard
packages. Devices like FET's and SCR's are also of importance in certain types of application and will be considered later in the article.

TRANSISTOR functioning as a switch differs from one
as a linear amplifier in one important respect: the operating point. As a switch, the tran-

-it

is either "on" (conducting)
sistor has two stable states
or "off" (non -conducting) Ideally, when in the "on"
state, the transistor collector-emitter voltage drop is zero;
when `off ", the collector current is zero. Junction transistors designed for switching can be made to approximate
these ideal states to a remarkable degree. In linear amplifiers, like a transistor biased in class A, collector current
always flows and an important objective is distortionless
operation.
The two basic switching modes are saturated and nonsaturated. In saturated switching, when the transistor is
in the "on" state, the collector -base ,junction becomes
forward biased and the collector -emitter voltage, b't.H(x.4T)'
is typically less than 0.q. volt. In non -saturated switching,
Nvhen the transistor is "on", the collector -emitter voltage
is greater than 1,',./.;(,,,r) and the collector -base junction
remains reverse -biased. Non- saturated switching does not
exhibit any storage time. Although the saturated switch
suffers from storage time (sec Fig. 1) . the average power
dissipation is less and the circuitry is simpler than for
non -saturated operation.
The transistor sold as a switch is different, for example,
from one which is marketed for linear operation at high
frequencies. In addition to low internal capacitances along
with a low- gain- bandwidlh product, a switching transistor
must also have very low storage tine.
To minimize storage tints, gold is added to the semi.

Table

A selection of some

TYPE
BV,

is typical of what is apThe input waveform of Fig.
plied to the base of a switching transistor in the commonemitter (CE) configuration. The CE connection is used
predominantly in digital computer and other switching circuits bcc:utse of its gain and phase inverting (not) properties. The output waveform is distorted and one can define
four delay times which limit the switching speed of the
transistor. Referring' again to Fig. 1:
1. Delay time, t,r: measured from the 10% point on the
input leading edge to the 10c.:; point on the output leading
edge. Delay time varies with CTJ. Cot,. Vno (Op and inversely with the turn -on base current, /in.
1

typical "n -p -n" and "p -n -p" switching transistors along with their characteristics.

-P -N SWITCHING TRANSISTORS

SWITCHING TRANSISTORS

2N2369A

2N3014

2N3724

2N3725

FK -1213

FT -1902

2N5057

2N5022

2N5023

30 -120

40 -120

60 -150

50 -125

30 -120

30 -100

40 -100

25 -100

50 -125

100-500
40
280

Optimum Ic(mA)

-20

10 -100

30 -120
30 -300

100-1000

100 -500

r,(nsec)

4
800

675

550

450

Fr(MHz)

P -N -P

FT -709

,:,,(volts)

hr,

Switching Parameters

-20

1200

10 -100

100 -1000

1200

40
230

-50

FK -1711

-20

1200

'Designed for non -saturated switching.

July, 1967

www.americanradiohistory.com

Open- circuit common -base output capacitance
Open- circuit common -base input capacitance
Crc.
Gain- bandw;dth product (frequency where hrI., = 1)
fT
Average value of common -emitter current gain
hrr
Collector- emitter breakdown voltage with base open
BVrro
Collector- emitter breakdown voltage with a specified reBVCICR
sistance in base circuit
I, Ro
Collector current with emitter open
Delay time
ta
Fall time
ti
Rise time
ti
Storage time
Turn -on time = t,( + tr
Turn -off time = L + tf
teer
Reverse bias voltage on base -emitter junction
VReoo
VRLI(SAT) Forward bias voltage on base -emitter junction with tranC,,,,

VEG(SAT)
Tn

sistor in saturation
Collector-emitter voltage with transistor in saturation
Storage time constant

Table 2. Important parameters for switching transistors.

90%

INPUT WAVEFORM

Variation in transistor delays with collector current are
shown in Fig. 4A. Over a wide range of collector current,
the delays t,(. t,.. and tf fall with increasing current and t5
rises somewhat with increasing current. In characterizing
a device for switching performance, it must also be
recognized that rise, fall, and storage times are functions
of hpE and B1'(.E,,. In general. as Il 'E and BI "(.E0 increase, the storage time increases too. Further, high beta,
high voltage, and fast snitching speeds tend to be mutually exclusive. High beta. low voltage and low beta, high
voltage come naturally.
For example. referring to Table 1, types such as the
FT -709 and FT -190'2 have few peers if speed is the sole
criterion. However, both are 6 -volt units and perform best
in the 1 -°?0 mA range.. more appropriate choice might he
a type such as the '21'23691 or its p -n -p counterpart, the
215057. These devices perform best ill the 10 -100 nA

200

10 O/o

100 ,

700

OUTPUT WAVEFORM

1o%
50

%
20

-4- to!!
input and output waveforms produced in
circuit that uses a saturated transistor switching element.
Fig. 1. Typical

10
7

c?. Rise time, t,.: measured from the 107r point on the
output leading edge to the 90% point on the output lead-

.. C_..-III/omml.
rdinnmom

)

paring different snitching transistors with respect to
storage time. The curves of Fig. :3 are examples of -70 as
a function of collector current for typical switching transistors. Knowing the r,, of a transistor at a specified
collector current, the storage time t,0 can be predicted
from Fig. '2. For example, if T, = 10 us and /111// 110 = ?, it is
found from Fig. that t,,.
15 ns.
.mother important parameter is the reverse leakage
current, I((;(,. This current almost doubles for every 111 °C
rise in temperature. The lower the value of Id.(;0, the
better the transistor approximates an ideal switch when
the transistor is in the "off" state. With the high quality
diffused -type transistors available, the reverse leakage
current does not usually provide any problems except at
very elevated temperatures.

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ing edge. Rise time varies inversely with hEE and with IT.
3. Storage time, t.,: measured from the 90rc point on
input trailing edge to the 90r.'ß point on the output trailing edge. Storage time varies with r0, the storage time
constant, and the ratio of the base turn -on /turn -off
(I((t /If(,O currents (see Fig. "2).
4. Fall time, tf: measured between the 90(;' and 10%
points of the output trailing edge. Fall time varies with
Co, and inversely with IT and 18.2.
In addition, one can define torn -on time (t,,,,) as the
sum t)) + tr and turn -off Iliac
ff) as the sum t. + tf.
The storage time delay, t., occurs only in saturated
switching. For this mode of operation, excess minority
carriers are stored in the base and collector during the time
the transistor is in the "on" state. When the transistor is
terued "Off", it takes time for the excess charges to recombine; this is the storage time.
The storage time constant parameter. 7,, is measured
with the collector current Ir and the turn -on and turn0;7 currents if;7 and 162, respectively, equal. Because it
is widely used. 70 serves as a useful yardstick for com-

,,,--®

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3000

Fig.

2. Curves for predicting storage times of transistors.

Fig. 3. Variation of storage time constant as a function

of collector current for a number of switching transistors.
40

ri.T

i,l

-f
1

;

rl
_1_:.

1
1
I

243002

253725

lei1tu

253304
255057
14330

IT?
)

13)a
5

50 70 100
20
COLLECTOR CURRENT -reA

200

500 700 1000

ELECTRONICS WORLD

range and have higher breakdown voltage ratings, but, of
necessity, are somewhat slower, especially at low currents.
The important message to the user is not to insist on
superlatives in all parameters. Devices that have such
attributes are either non -existent or such a small part of
the normal distribution that their price would be high
and reproducibility in large quantities difficult. Part of
the confusion is caused by the device manufacturers themselves. Two or three data sheets are often written for one
basic product type. They usually represent different parts
of the distribution, the most exotic device being the most
expensive. What is often not visible to the user is that the
price is high, not because the parameter limits are necessarily superior, but because the yield is low.

RTL

DTL

CML

High BVru0

Medium BVc1,o

High operating

current
High VBE(SAT)
High hFE
with tight spread
Moderate hFE

Low Cob

Low T.

Low T,

Low Co)

High collector
Low T,

dissipation

Lower operating
current than
for RTL

Low C,,,,
Low CTE

Table 3. Important device requirements for transistor logic.
30
25

Making the Selection

220

The diffused transistor in its many forms is the transistor most commonly used for switching. These devices
are fast and can be produced in large quantities at low
cost. Where fast switching speeds are not important, alloy -type transistors can be used if they are cheaper than
the diffused device. With some alloy switching transistors,
-the saturation voltage VCE(a.AT) is less than 50 mV, making them well suited for direct -coupled transistor logic.
In some high-speed switching circuits, germanium rather
than silicon devices are employed. However, for conservative operation, the junction temperature of a germanium
transistor cannot exceed 80 °C; for silicon, the upper
limit is 125 °C.
The popularity of saturated switches stems largely from
the fact that their average power dissipation is low and
their design is fairly straightforward and predictable.
However, everything is not in favor of the saturated
switch. Storage time is a serious problem and in the
saturation region, COt, and IT degrade quite severely.
The non- saturated switch avoids this degradation and
storage time by keeping the operating point away from the
saturation region. The net result is that devices such as
the FK -1213 and FT-1711, especially designed for this
operating mode, can have total switching (turn -on plus
turn -off) times of less than 2 nsec. One of the prices paid
is increased dissipation, a feature that tends to preclude
use of non -saturated operation in integrated circuits. Current mode logic, which uses non -saturated switching,
requires voltage level translators in the form of emitter followers. Types like the FK-1213 and FT-1711 are used
in this logic. These transistors are mirror -image devices
and, when used together, level translation is not required.
Another mode of operation is avalanche mode switching.
As the reverse collector-emitter voltage of a transistor
is increased, a point is reached where the transistor begins to operate in the avalanche mode (Fig. 4B) . This
is similar in operation to a reverse -biased diode, such
as a zener or reference diode. From Fig. 4B it is noted that
after breakdown, a negative region exists, i.e., as the
collector voltage falls below BVcER, the collector current rises. If a load resistance, RL, is chosen so its load
line intersects the negative- resistance region between
points X and Y, the transistor is operating as an avalanche mode switch. The output voltage swing is Vy
v volts and extremely fast switching speeds (turn -on
plus turn -off) of less than 1 nsec can be realized. However, the average device dissipation is greater than
for conventional saturated and non -saturated modes of
operation.
The FET and its kin, the 1IOSFET and IGFET, can
also be used to advantage in some discrete switching
applications. Chief among these is their use in choppers
where their low offset makes them superior to junction
transistors. In general, the field- effect transistor has not
displaced the bipolar transistor primarily because of its

DCTL

Low VCE(SAT)

I-

5
010
50 100 200 500
20
COLLECTOR CURRENT(Ic) rnA

(A)

(Al Dependence of transistor delays on collector current. (B) Operating region for avalanche mode switching.
Fig. 4.

(A)

(B)

(C)

(D)

Fig. 5. Examples of transistor logic circuits shown
here include (Al DCTL, (B1 RTL, IC) DTL, (DI CML.

relatively high "on" state dissipation and poorer switching speed.
At high -power or high- voltage levels, the SCR starts to
look attractive for power conversion applications. At
lower levels, however, the commutation problems and
poorer switching speeds give transistors a decided edge.

Transistor Logic Requirements
Different types of transistor logic circuits are realized
by changing the coupling element between transistors.
These coupling elements are either direct connections,
resistors, diodes. or resistor- capacitor combinations. The
four most popular logic forms used with discrete components are: DCTL (direct- coupled transistor logic) ,
RTL (resistor -transistor logic) , DTL (diode- transistor
logic) , and CML (current mode logic) Table 3 lists the
important device requirements for these four forms of
.

logic.

The breach between integrated and discrete logic circuits is widening. Passive elements with tight tolerances
and dissimilar device characteristics are no problem for
discrete components. These constitute formidable obstacles
in integrated form and this has led to modification of

July, 1967

www.americanradiohistory.com

these logic forms and to the evolution of completely different classes of logic.
In DCTL, the collector of one device couples directly
to the base of another, as shown in Fig. 3A. Its advantages
are: simplicity, minimum of components required, low
cost, and the fact that only a single supply voltage is
required. Its disadvantages include: low signal levels and
therefore sensitivity to noise, strong dependence on uniform device characteristics, and switching speed limited
by storage time.
Resistors perform the logic while the transistor serves
as the inverter in RTL (Fig. 3B). For cascading purposes,
the output is designed to be the same as the input sicle.
This logic is relatively simple, low cost, less sensitive to
variations in i'c.r,;rt_iT, and l'E(,y..cl,), and good noise
immunity. On the minus side. RTL has low fan -in and
fan -out capabilities, slow speed, and requires high signal
voltage levels. A variation of RTL, RCTL uses a capacitor across the coupling resistors. This results in faster
operation than RTL because the base sees a low impedance
both during turn -on and torn -off and the delays are
considerably reduced. However, noise immunity is poor
and transient loading can be severe.
In DTL, the resistors used in RTL are replaced by
diodes (Fig. 5C) This logic provides optimum use of
available base chive by avoiding the current -shunting paths
existing in DCTL and RTL. Also it has good noise immunity, fan -in capability, and is faster than RTL and
DCTL. One disadvantage is that, in saturation, the bases
of the following stages see a voltage equal to i-r'Etsaz)
plus the diode voltage drop. This means that a larger turnoff current is required. What is more, it is also costlier
.

than RTL.
The salient feature of

C_MIL is that it is the only logic
the four listed that is non -saturating. Referring to

Fig. 5D, the emitter current, IE, is relatively constant
and is switched from one transistor to another as the
signal to input 1, or '2, is varied. The variation in the
input signal is with respect to the reference voltage, V REF.
C:IL is a vei'v fast logic because it has no storage time,
very good noise immunity, and a high fan -in. The price
paid for this superior performance is high power dissipation and a requirement for level translation. In addition,
many transistors are required, making the cost high.

Future Possibilities
Regarding performance, no major breakthroughs are
anticipated in the near future. The market incentive is not
there for low -level discrete applications: logic functions
have been taken over by integrated circuits. Integrated
semiconductor technology is particularly suited for producing large numbers of identical circuits with unprecedented reliability. making them naturally compatible with
computer circuits.
In power applications, the discrete switch will remain
on the scene longer because of the heat dissipation problem. In memory applications, for instance, device dissipation is considerable. There is a need for further
improvements in discrete drivers for memory elements. As
computers become faster, memory cycle times are reduced,
thus imposing more stringent requirements on the switching tinges of the semiconductor drivers.
Increased automation and improved yields have already
caused prices to drop steadily. Refinements in processes
and other developments have greatly enhanced reliability.
Prices will continue to drop because the semiconductor
business is highly competitive and reliability will continue to improve largely because of the increasingly
stringent demands of the military and large computer
manufacturers.

HIGH-VOLTAGE TRANSISTORS

HOW MANY TRANSISTORS?

tend to think of transistors as low- voltage devices even though
some of the newer types reaching the market are capable of operating safely with approximately 1000 volts applied to them.
Advanced diffusion techniques, coupled with other proprietary operations, have enabled the M.S. Transistor Corp. to announce a new
family of high -voltage silicon "n -p -n" transistors which includes the
2N5010 through 2N5015 (2 -watt units), and MST -50 to MST -100 (also
2 -watt units), and the MSP -50 to MSP -100 (5 -watt units).
Operating voltage of the new transistors ranges from 500 to 1000,
reaches 500 mA, h,,; is between 20 and 180, and the transistors are
capable of operation to 35 MHz. The MST -xx and 2N50xx series come
in TO -5 cans, while the MSP version comes in an MD -14 case.
These new high -voltage transistors open many new areas formerly
the sole province of the vacuum tube, for example, the relatively high voltage deflection circuits for electrostatic CRT's. In addition, many
conventional circuits can now be extended. In the case of these transistors, they can be operated from a 120 -, 240 -, or 480 -volt a.c.
power line and require only a full -wave rectifier and capacitor filter.
They would also be useful as EL panel drivers as the devices can be
used to drive the essentially capacitive loads by running class -A stages
in series push -pull configuratons.
In the area of consumer electronics, the Delco Radio Division of GM
Corp. has announced its high -voltage transistor (DTS -0714) having a
VCEK of 1200 volts, V c,srs, of 750 volts, linear current gain (ht-,.,) at
2.5 amperes of 10 min.mum, and a reverse voltage (Vr,,,o) of 5 volts.
The new sil:con, tripe- diffused, mesa transistor has been used in
switching the 3800 volt- ampere load of a 25 -inch color -TV horizontal
sweep deflection circuit.
In the TV circuit, a 1050 -volt pulse is transformed in the flyback
transformer to 25 kV for use by the CRT. The horizontal output transistor swatches about 4 amperes during this operation, and is protected
from arcing by a diode and RC network.
The transistor, which replaced a pair of 700 -volt types used previously (DTS -402), and a vacuum tube before that, is presently available in a strip- mounted epoxy package.

THE chip shown below, although designed as an integrated circuit,
dramatically illustrates the density attained by modern diffusion
techniques. The chip is 58 mils square and, as shown, only a portion

of it is used for the 415 "p "- channel enhancement -mode transistors.
Fabricated by General Instrument's Microelectronics D vision, the
chip is a 64 -bit serial accumulator capable of operation to 5 MHz. The
company is presently embarking on a program having an expected
density of up to one million transistors per square inch. They have already produced devices having 250,000 transistors per square inch. A

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A timely forecast of the
excitement -packed 1967 season
-by the editors of Skiing Magazine.
1967
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July, 1967

www.americanradiohistory.com

OlIN FRYE
Solid -state devices have materially changed amateur radio
equipment, and even greater improvements appear imminent.

HAM RADIO AND SEMICONDUCTORS
WHEN thunder from the July storm started to roll,
Mac and Barney grounded the antennas, opened
the service bench switches, and started for the
front office to comfort Matilda, the office girl, who was deathly afraid of thunder and lightning. Just as they stepped
through the door there was a blinding flash of light followed
almost immediately by a snapping sound and a great bellow of thunder.
"To quote Thomas Hardy: `How can such a heavenly light
be the parent of such a diabolical sound ?' " Matilda asked
with a nervous giggle. "Why don't you two talk about electronics? That always quiets my nerves. In fact, it usually
bores me so much sleep comes as a defense mechanism."
"Always glad to oblige a lady," Barney replied, perching
himself on a corner of her desk. "Mac, I've been wanting to
talk to you about the love affair hams have with semiconductors. Right from the beginning, those two have gone together like guitars and folksingers, and you don't need a
crystal ball to see a lot more conventional and exotic semiconductors in the future of ham radio."
"It's not hard to understand why hams would take to solid -state diodes and transistors," Mac mused. "For one thing,
the tiny size of these devices goes along with the modern
trend toward more compact and lighter amateur radio gear.
I can remember a few years back when a kilowatt ham
transmitter was a truly impressive affair, occupying two six foot racks and weighing upwards of half a ton. But the
days when a ham could take over a spare upstairs bedroom
or the basement for his ham shack are going fast. The
average small, functional, modern house doesn't have a spare
bedroom; and if there is a basement, it's likely serving as a
playroom or bar. Today's ham has to make do with a
corner of the living room, den, bedroom, or even the kitchen. To meet his needs, the modern kilowatt radio station
has been compressed until it fits neatly on a table top and
weighs less than a hundred pounds."
"You're right, of course, but it's only fair to say that the
switch from AM to SSB transmission accounts for much of
this saving in weight and size. In that kilowatt AM station
you were talking about, one of those six -foot racks held
speech amplifier and modulator equipment, together with
the husky power supply needed for the latter. Getting rid
of the modulator cut the size of the transmitter in half.
Since an SSB transmitter need not supply a power- consuming carrier, it imposes much less demand on the power
supply. Current peaks drawn under modulation are of very
short duration so that the average demand on the power
supply, even when the transmitter is inputting 2 kW p.e.p.,

modest."
"I know," Mac said. "I never cease to marvel at how
those table -top linears can get around 3000 volts out of a
transformer only slightly larger than the power transformer
for a color-TV receiver. Of course, I know it's done by using
voltage -doubling circuits employing series -connected silicon
rectifiers. You certainly couldn't do it if you had to use meris

cury -vapor 866's for rectifiers. Their filament transformer
alone would take up more space than all the silicon diodes
and would weigh a whopping lot more."
"Silicon and germanium diodes replace bulky tubes lots
of other places in SSB transmitters and receivers," Barney
said. "They are used as audio rectifiers in the vox and anti trip circuits and in the balanced modulators that suppress
the carrier, and as r.f. rectifiers in the automatic level -control circuits that limit drive to the linear amplifiers so as not
to exceed what the amplifier can handle in a linear fashion.
A diode rectifies a sample of the r.f. output and feeds it to a
milliammeter to provide an r.f. output indicator. Other
diodes provide a.g.c. voltage for the receiver or transceiver.
Zener diodes provide voltage regulation of critical low voltages in the vox and other circuits."
"How about transistors? Are hams making much use of
them ?"
"So far, they have used transistors chiefly outside the station receiver and transmitter. The first uses were for code
practice oscillators and mike preamplifiers, including speech
clipping and limiting circuits. But lots of hams have been
experimenting with flea -power transistorized transmitters
and with transistorized communications receivers. As far as
completely transistorized transmitters are concerned, the
chief stumbling block has been a lack of reasonably priced
transistors that can efficiently handle a couple of hundred
watts input up to 30 MHz. I know there are transistors that
can do this, but they are not available to hams, at least not
at a price they can afford. While I keep hearing rumors
about other solid -state transceivers on the drawing boards,
as far as I know there is only one amateur -band transceiver on the market that is completely transistorized-ex cept for the final amplifier tubes."
"Well, how about receivers? We have plenty of transistors that can handle any power requirements there."
"True, but again there are drawbacks -or have been until
very recently. The ordinary transistor is essentially a small signal device. When one is used in the r.f. stage of a
communications receiver, it will do a fine job of amplifying
weak signals until a nearby ham fires up a full gallon on the
same band. Then his signal overloads the input of the transistor with resulting cross -modulation that does an excellent
job of swamping out the weak station. If that weak station
happens to be a rare ZA in Albania or a YI in Iraq, the ham
is likely to be very disturbed-to put it mildly!"
"I suppose you're thinking about the FET and its ability
to handle both strong and weak signals as the answer to this
problem."
"Right you are, and I see no reason why an excellent,
fully transistorized amateur receiver cannot be built right
now. It would have many advantages, including such things
as small size, light weight, practically no generation of heat,
indefinite transistor life as opposed to comparatively short lived tubes, resistance to shock and vibration, and simple
power -supply requirements that could be easily and ecoELECTRONICS WORLD

www.americanradiohistory.com

IlsïION,QnR-ROW ®R ELRJe

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"Sound For A Picture Evening, Volume II"
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"Sound For A Picture Evening,
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is enclosed.
My check (or money order) for $
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"SOUND FORA PICTURE EVENING, VOLUME I" still available
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backgrounds and 8 tracks for special sound effects. Please
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per record ordered.)
I

July, 1967

www.americanradiohistory.com

nornically met by batteries for mobile
or portable operation."
"Well, I'll hazard a guess that if U.S.
manufacturers don't get on the stick
and come out with something like this
at a reasonable price soon, they vvill be

... not hy
a long shot

it isn't!!
There's certainly nothing top secret
about the classified pages in Electronics World Magazine. They're
wide open to the searching eyes of
every buyer who's in the market
for the product or service that he
knows can be found in Electronics
World's Electronics Market Place.
The more than 191,000 buyers of
Electronics World, largest readership of any magazine for electronics
professionals in the world, are your
guarantee of knowing that your ad
is being read by people who are
constantly looking for and buying

electronics products. It is these
people to whom you MUST direct
YOUR advertising as do the many
key advertisers appearing in this
issue and in each issue throughout
the year.

it- there's a vast
market of buyers searching the
classified advertising pages of Electronics World and it's important
that your ad be exposed to this
prime buying audience. Prove to
yourself that the leading magazine
for electronics professionals MUST
ALSO be the leader in sales responses to the many classified ads
presently enhancing its pages it
makes a great deal of sense -give
No doubt about

it a try.

There's complete rate information
for your convenience in the classified section of this issue. Or, if you'd
like a little personal service, it's
right up our alley. Just write to
HAL CYMES
Classified Advertising Manager
ZIFF -DAVIS PUBLISHING COMPANY
One Park Avenue
New York, New York 10016

scooped by the Japanese."
"You can say that again. I think the
Japanese are beginning to eye the ham
market the way they did the CB market, and are both know what they dici
there in the way of transistorized transceivers. Quite recently, I've run across
several DX stations who say they are
using Japanese -made ham equipment.
One thing is sure: the number of Japanese amateurs is increasing rapidly. It
used to be you had to listen long and
hard to hear a JA station, but now just
about any time I point my beans northwest I hear Nippon stations coming ill
On ten, fifteen, or twenty meters -and
with darned good signals, too. Some of
the fellows on the islands out ill the Pacific complain that the Japanese are beginning to swamp them out the way
1..S. hams monopolize the bands in
this hemisphere."
"These things sound like straws in
the wind to tae," Mac said. "We have
long produced most of the manufactured ham equipment, probably because the great majority of the world's
radio amateurs are located in this country. In no other country lias the home
ham market been large enough to warrant the research and development necessary for producing this highly specialized equipment. Now, with the ham
populations of other countries on the
rise and with Americans' ready acceptance of imported electronic equipment,
this may be changed."
"Hey, that brings up an interesting
chat I had with a ham in The Nether lands the other morning. He suggested
dart the number of active hams ill a
country compared to its total population was a good index of that country's
electronics know -bow and its ability to
produce electronic gear. He pointed out
the high percentage of hams in Englund, West Germany, Japan, and the
United States us examples."
"He may have something there. We
both know that the electronics industry has always displayed an interest in
amateur radio that goes beyond that
segments being an important market
for electronic products. Take a look at
the applications section of any diode,
transistor, grid -controlled rectifier, or
integrated -circuit manual, and you will
find several strictly ham suggestions.
And hams return the compliment.
Practically every one of their magazines
Lis a regular semiconductor column, or
nmething similar, in which new semi c.onductor devices are introduced or cirIlUts involving semiconductors are de-cribed. In addition, ham magazines
illten carry full -length feature articles

describing the use of semiconductors in
ham gear written by top men involved
in the production, research, and development of solid -state devices. This
is not surprising, considering how many
of these people have ham radio for a
hobby."
"That brings up an important feature of solid -state devices. They lend
themselves to experimenting, home
construction, and kit construction. Transistorized gear is almost invariably assembled on a printed- circuit or Vector
board. You don't need a machine shop
to bend chassis, punch socket holes, or
cut out heavy metal areas as you ordinarily do when building equipment
using tulles. What's more, since distributed capacitances are easily duplicated with this type of construction, you
can build a piece of equipment from an
article and expect equivalent performance. The use of 1C's is going to
make this even more true. No wonder
hams who like to build and experiment
are in love with transistors!"
"Okay; let's not get carried away.
How do you picture transistorized ham
equiputetit of the future ?"
"Well, there's a limit to how much
you can reduce the panel area of a
ham transceiver. No natter how small
the components behind that panel, you
still need room to mount all the controls, jacks, dials, and meters necessary for operation. The panel of my
present transceiver carries fifteen of
these components. Since many controls
require a comparatively close adjustment, the knobs cannot be made too
small. The tuning dial, for instance, has
to be large enough for fine adjustment
and for comfortable operation hour
after hour. The meter and frequency
indication must be large enough for easy
reading. So 1 see the ham transceiver
of the near future as not much smaller
in height and width but greatly reduced
in depth.
"The use of FET's and IC's will produce better, more sophisticated, more
trouble -free equipment. The lower voltages required by transistors and their
lack of heat generation will greatly reduce component failure. Alobile operation, already stimulated by SSB, will
increase even more when solid -state
transceivers with their low current requirements are in Nvidespread use. We
may still have to use compact ceramictype tubes in high- powered linears, but
medium -power transmitters and exciters will be fully transistorized and will
take up touch less space than today's
equipment -"
His voice trailed off as he nodded
to Alatilda, sound asleep with her bead
resting on her folded arras on her desk,
oblivious to the intermittent growls of
thunder from the retreating storm.
"I thought she was kidding!" he said
in a hoarse vvhisper to \
WORLD

www.americanradiohistory.com

SERVICE MASTER

HANDIEST

RADIO

HANDFUL

TV NEWS

of service tools

THE engineers at Television Hanufacturers of America have a gripe,
and it is a real one judging by the experience of others.
After visiting a number of color -TV
demonstration showrooms, they ( and
we) noticed that reception in multi-set
demonstrations of large dealers often
leaves much to be desired.
According to the TMA chief engineer, "Poor tuning of sets on the showroom floor creates as much sales resistance as anything, including the high
price of color sets.
"The colors run together, and often
the purity and convergence are so poor
that colors are quite the opposite of
what viewers know they should be
in many cases, every figure is surrounded by a reddish halo.
"Big dealers by their very bigness are
particularly vulnerable to this problem.
They often tend to have too marry sets
playing at one time to pay attention to
each set's fine tuning (and color setup).
Thus, a customer sees a variety of colors
for the sane program."
Many potential customers who overlook bad showroom quality in monochrome sets, seem to know instinctively
that the set is not at fault, but balk at
baying tvhelr the same trouble shows
up in a color set demonstration. There
are two reasons for this. First, the main
attraction of color-TV is color itself. If
the customer is not impressed, he sees
no reason to change from monochrome.
Second, a small percentage are convinced that color is still too primitive.
Both views are mistaken, but poor quality in a demonstration set tends to support each belief.
.

Portable VTI.
The Ampex Corp. recently_ demon-

strated

battery -powered

portable

video tape recorder measuring 23 by
13 by 6 inches and weighing only :35
lbs. In its attaché-type case, the unit is
mounted on a back pack to enable onthe -spot video tape recordings to be
made by news agencies. The new VTR
can record up to 20 minutes of action
on an 8-inch reel and is compatible for
direct re- broadcast over conventional
studio tape decks.
A companion camera weighing 13

lbs. complete witl its own electronic
view -finder is also 'ncluded in the package. A built -in clock keeps the operator
aware of remaining recording time.
Laser Activities

Engineers at GT&E recently demonstrated a liquid laser about as thick as a
fountain pen and six inches long capable of generating a burst of light energy equivalent to one million watts
(10,000 hundred -watt light bulbs)
In this new laser, the medium is
.

formed by dissolving neodymium (a
rare earth) in selenium oxychloride
(an inorganic compound). The whole
process takes about ten minutes to corn plete. An external flash tube provides
the excitation for the laser.
In another use of the ubiquitous
laser, scientists at TRW Systems Group
are using laser holography to record
microscopic phenomena moving a few
millionths of an inch ill less than one
millionth of a second. The flights of
fruit flies (gnats) and bullets have been
"stopped" at 100 billionths of a second
and recorded on a 4 x 5 inch photographic plate. And, for the first time, a
photographic portrait was taken of a
mixture of air and acetylene the instant
it was detonated by a spark.
Both TRW and other agencies are
exploring the possibility of many new
breakthroughs because of this new
technique. Of course, all images made
using the hologram technique are three dimensional.
Canine Detection
While other countries are looking
towards electronics as a means of detecting buried ore deposits, a small
item in the Soviet journal Razredka
i Ok/uauo Nedr (Exploration and Conservation of Resources) seems to hear
looking into.
It seems that the Soviets now llave
canine comrades that have been trained
to sniff out ore deposits buried under
seven feet of earth. These animals are
also capable of detecting some ores at
even greater depths.
It is assumed that in the vast, still
unexplored areas of Central Russia,
clogs are easier to come by than batteries.
A

23 essential tools at your fingertips in this lightweight (only 23/4 lbs.), compact, easy-to- carry,
roll -up kit. Contains long nose plier, diagonal
plier, adjustable wrench, regular and stubby
plastic handles with these interchangeable
blades: 9 regular and 3 stubby nutdriver, 2
slotted and 1 Phillips screwdriver, 2 reamer, 1
extension. Eyelets in plastic- coated canvas case
permit wall hanging. New elastic loop secures
roll, eliminates need for tying.

many optional accessories:
Junior and Tee handles ... Additional nutdriver,
Phillips & slotted screwdriver, and extension
blade sizes ... Allen hex type, Bristol multiple
spline, Frearson, Scrulox, and clutch head blades
...Awl /Scriber...Chuck adaptors to use blades
in spiral ratchet drivers.
WRITE FOR CATALOG 166

XCELITE, INC., 12 Bank St., Orchard Park, N. Y. 14127
In Canada contact Charlra W.

Pointon, Ltd.

CIRCLE NO. 96 ON READER SERVICE CARD
65

July, 1967

www.americanradiohistory.com

Neutralizing the

Build your own

AUTO ANALYZER
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Gascode Amplifier
By LEE R. BISHOP

Using a conventional signal generator instead of a
noise generator to adjust this widely- used front
end circuit for nrininlrun noise within its passband.
1HE cascode circuit

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zio -code

tralized, however, L,, will form a parallel
resonant circuit with the grid -to -plate
capacitance of V1. This circuit should
be resonant at the amplifier center frequency; consequently, minimum signal
will appear at the output of the cascode
circuit. If a v.t.v.m. or some other sensitive indicating device is connected to
the output of the cascode circuit, tisis
minimum will show up as a rather broad
clip in amplifier output when the signal
generator is tuned through the frequency of interest. If the dip does not
occur at the proper frequency, the signal generator should be tuned to the required center frequency and L adjusted
for minimum Output.
The actual point in a complete receiver used to detect the dip will depend
upon the sensitivity of the device that
is employed as an indicator. To prevent
the effect of the i.f. response of succeeding stages from obscuring the dip, it
should be detected as close to the output of the cascode amplifier as possible.
The optimum point for detection would
be 12, but because of sensitivity limitations in practical detecting equipment,
the clip will normally have to be detected two or three stages of amplification after J2.
If large numbers of amplifiers were
to be neutralized quickly by this method,
a special tube with its cathode pin
clipped off could be used. The clipped pin technique, however, will not produce nearly as good an alignment
because of the variation in tube capacitance found in actual practice.
Fig. 1. Basic arrangement of a cascade

circuit

showing

neutralizing

coil

L,,.

Method Used
Neutralization is accomplished by

y
"I

Payment enclosedYou get 1 extra issue
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is a two -stage
vacuum -tube triode amplifier that
his the gain and stability of a pentode
but the noise figure of a triode. It is almost universally used in u.h.f. /v.h.f.
communications gear, radar receivers,
mid quality TV sets as an r.f. or i.f. amplifier. A basic version of this circuit as
commonly found in front -end stages is
shown in Fig. 1.
The plate circuit of the first triode
amplifier (V1) works into the extremely
low impedance presented by the cathode
circuit of V2 and is loaded heavily
enough to give a first -stage gain of unity
or less. This severe loading provides sufficient damping to completely eliminate
any possibility of oscillations in the first
stage.
First -stage stability notwithstanding,
a neutralizing coil (L
is invariably
included in most cascode circuits because the amplifier noise figure is greatly improved when the grid -to-plate
capacitance of the first stage is neutralized at the center frequency of its
passband. Neutralizing coils with a "Q
in the vicinity of 200 have been found
to provide the best noise figures. When
a receiver alignment is being performed,
one adjustment that is not made with
gain or passband in mind is that of the
inductance of L,,. This coil is adjusted
Ii r best amplifier noise figure with the
aid of a noise generator.
Such instruments, however, are not
common, but conventional signal generators are. By employing a variation of
the familiar neutralizing procedure used
in transmitter tuning, a conventional
signal generator can be made to substitute for a noise generator and enable
a respectable job of cascode -amplifier
neutralization for best noise figure to
be performed.
T

disconnecting the cathode lead from the
tube socket of the first cascode stage
(VI) and injecting to the input a c.w.
or amplitude -modulated signal at the
operating frequency of the cascode circuit. Strong signals can pass from the
first to the second stage through the
grid -to -plate capacitance of V1. If the
cascode circuit has been properly neu-

INPUT

ouTPut

TO
MIXER OR
I.F. AMP.
J2

ELECTRONICS WORLD

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Why settle for less? Buy the Best!

Static Electricity
(Continual fruin page 23)

THE FABULOUS

Anti- Static Sprays. These sprays apply a chemical coating which forms
a conductive surface. The anti -static
agents can be incorporated directly into plastics; liquid household bleach
bottles often include such agents since
merchandisers have found that dust covered packages are a sales handicap.
Drag Chains. Years ago, safety engineers thought that drag chains on gasoline trucks would bleed dangerous
static charges back to the road as fast
as they were generated. Now the National Fire Protection Association says
that a drag chain is ineffective for this
purpose when the road is dry, and it is
not needed when the road is wet.
Helicopter Static Discharger. Friction from air currents can cause helicopters to acquire a static electricity
charge which may be quite dangerous:
it can cause volatile flammable liquids
on board to explode or cause explosives
on military aircraft to accidentally ignite.
D,nascience-s Corporation has developed an aircraft static electricity discharging system which has effectively
eliminated these hazards. With this
system, a low- voltage unit senses the
charge on the helicopter and its polarity,
amplifies and compensates this signal,
and, depending upon the polarity of
the charge on the helicopter, drives
either a positive or negative high -voltage generator in order to compensate
for the charge.

CAPACITIVE DISCHARGE

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tive charges come back down the belt.
The larger the sphere, the greater the
voltage that can be obtained. Conversely, the smaller the sphere, the smaller
the possible voltage. Such generators
are widely used in research laboratories.
July, 1967

any vehicle. Racers

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A Improved gasoline mileage
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Portable, high- impact case for
rugged work

Advantages of Static Electricity
With all its faults, can anything good
be said about static electricity? Yes. It
can definitely be put to work in electrostatic painting systems and in Van
de Graaff generators which are used in
atomic research.
In electrostatic painting, paint droplets are given an electrostatic charge as
they pass through an atomizer. Since
the paint then tends to converge on the
item to be painted, it simplifies the job
of painting the back sides of cylinders
and knobs. Also, very little of the paint
is lost in the process; some electrostatic
paint installations claim that paint consumption is 30% that of a standard
painting installation.
The Van cue Graaff generator consists of a belt traveling over plastic
rollers, a charge source, and a metal
sphere. Charges are carried up the belt
to the sphere where they collect; nega-

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CuRCLE NO. S4 ON READER SERVICE CARD

1
67

www.americanradiohistory.com

50 functions in a single chip. The functions of 50 separate transistors, diodes, resistors and capacitors can now be formed by the
tiny dot in the center of the integrated circuit held by the tweezers.

The "Chip"
...wild it make or

your job future?

THE DEVELOPMENT OF INTEGRATED CIRCUITRY
is the dawn of a new age of electronic miracles. It
means that many of today's job skills soon will be
no longer needed. At the same time it opens the

door to thousands of exciting new job opportunities for technicians solidly grounded in electronics
fundamentals. Read here what you need to know
to cash in on the gigantic coming boom, and how
you can learn it right at home.

each no bigger than the
head of a pin, are bringing about a fantastic new
Industrial Revolution. The time is near at hand
when "chips" may save your life, balance your
checkbook, and land a man on the moon.
Chips may also put you out of a job... or into a
better one.
"One thing is certain," said The New York Times
recently. Chips "will unalterably change our lives
and the lives of our children probably far beyond
recognition."
A single chip or miniature integrated circuit can
TINY ELECTRONIC "CHIPS,"

break

perform the function of 20 transistors, 18 resistors,
and 2 capacitors. Yet it is so small that a thimbleful
can hold enough circuitry for a dozen computers or
a thousand radios.
Miniature Miracles of Today and Tomorrow
Already, as a result, a two -way radio can now be
fitted inside a signet ring. A complete hearing aid
can be worn entirely inside the ear. There is a new
desk -top computer, no bigger than a typewriter yet
capable of 166,000 operations per second. And it is
almost possible to put the entire circuitry of a color
television set inside a man's wrist -watch case.
And this is only the beginning!
Soon kitchen computers may keep the housewife's
refrigerator stocked, her menus planned, and her
calories counted. Her vacuum cleaner may creep out
at night and vacuum the floor all by itself.
Money may become obsolete. Instead you will
simply carry an electronic charge account card. Your
employer will credit your account after each week's
work and merchants will charge each of your purchases against it.

ELECTRONICS WORLD

www.americanradiohistory.com

When your telephone rings and nobody's home,
your call will automatically be switched to the phone
where you can be reached.
Doctors will be able to examine you internally by
watching a TV screen while a pill -size camera passes
through your digestive tract.
New Opportunities for Trained Men
What does all this mean to someone working in electronics who never went beyond high school? It
means the opportunity of a lifetime -if you take advantage of it.
It's true that the "chip" may make a lot of manual
skills no longer necessary.
But at the same time the booming sales of articles
and equipment using integrated circuitry has created a tremendous demand for trained electronics
personnel to help design, manufacture, test, operate,
and service all these marvels.
There simply aren't enough college -trained engineers to go around. So men with a high school education who have mastered the fundamentals of electronics theory are being begged to accept really
interesting, high -pay jobs as engineering aides, junior engineers, and field engineers.
How To Get The Training You Need
You can get the up -to -date training in electronics
fundamentals that you need through a carefully
chosen home study course. In fact, some authorities
feel that a home study course is the best way. "By
its very nature," stated one electronics publication
recently, "home study develops your ability to analyze and extract information as well as to strengthen your sense of responsibility and initiative." These
are qualities every employer is always looking for.
If you do decide to advance your career through
spare -time study at home, it makes sense to pick an
electronics school that specializes in the home study
method. Electronics is complicated enough without
trying to learn it from texts and lessons that were
designed for the classroom instead of correspondence training.
The Cleveland Institute of Electronics has everything you're looking for. We teach only electronics
-no other subjects. And our courses are designed
especially for home study. We have spent over 30
years perfecting techniques that make learning electronics at home easy, even for those who previously
had trouble studying.
Your instructor gives your assignments his undivided personal attention -it's like being the only
student in his "class:' He not only grades your work,
he analyzes it. .And he mails back his corrections
and comments the same day he gets your lessons, so
you read his notations while everything is still fresh
in your mind.
Always Up-To -Date
Because of rapid developments in electronics, CIE
courses are constantly being revised. Students re-

ENROLL UNDER NEW G.I. BILL
All CIE courses are available under the new G.I.
Bill. If you served on active duty since January
31, 1955, or are in service now, check box on
reply card for G.I. Bill information.

Tiny TV camera
for space and military use is one of
the miracles of integrated circuitry.
Thi.r one weighs 27
ounces, uses a one inch vidicon cam-

era tube, and re-

quires only four
watts' of pouter..

ceive the most recent revised material as they progress through their course. This year, for example,
CIE students are receiving exclusive up-to- the -minute lessons in Microminiaturization, Logical Troubleshooting, Laser Theory and Application, Single
Sideband Techniques, Pulse Theory and Application, and Boolean Algebra. For this reason CIE
courses are invaluable not only to newcomers in
Electronics but also for "old timers" who need a
refresher course in current developments.

Praised by Students Who've Compared
Students who have taken other courses often cornment on how much more they learn from CIE.
Mark E. Newland of Santa Maria, California, recently wrote: "Of 11 different correspondence
courses I've taken, C1E's was the best prepared,
most interesting, and easiest to understand. I passed
my 1st Class FCC exam after completing my course,
and have increased my earnings $120 a month:'

Get FCC License or Money Back
No matter what kind of job you want in electronics,
you ought to have your Government FCC License.
It's accepted everywhere as proof of your education
in electronics. And no wonder -the Government licensing exam is tough. So tough, in fact, that without CIE training, two out of every three men who
take the exam fail.
But better than 9 out of every 10 CIE -trained
men who take the exam pass it.
This has made it possible to back our FCC License courses with this famous Warranty: you must
pass your FCC exam upon completion of the course
or your tuition is refunded in full.
Mail Card For Two Free Books
Want to know more? The postpaid reply card bound
in here will bring you a free copy of our school catalog describing today's opportunities in electronics,
our teaching methods, and our courses, together with
our special booklet on how to get a commercial FCC
License. If card has been removed, just send us your
name and address.

CIE
Cleveland Institute of Electronics
1776

17th St., Dept. EW -34, Cleveland, Dhio 44114

Accredited Member National Home Study Council
ALeaderin Electronics Training...Since 1934

CIRCLE NO. 122 ON READER SERVICE CARD

July, 1967

www.americanradiohistory.com

TEST
EQUIPMENT

PRODUCT REPORT

(9)1(3

iiíiir

1110111111111

11111111101111111

'SKI

Model 7050 Digital Voltmeter
For ropy on manufacturer's brochure, circle No. 36 on Reader Service Card.

NE of the hits of the recent IEEE
Show in New York was the compact digital voltmeter just introduced
by Fairchild Instrumentation. The meter is easily held in the palm of one
hand; it measures only about 6 inches
wide by 3 inches high by 7 inches deep
and it weighs just under 4 pounds.
More impressive than this, however, is
the price. The meter costs only 5249 in
quantities of 25 or more, or 8299 in
quantities of 1 to 4. The main reason
for the small size and low price (for a
DV\I) is the use of the company's integrated circuits in the instrument.
The Model 7050 is a "31/2- digit" meter. This indicates that there are three
full decades, each with its indicator
digit, plus a fourth digit ,indicating an
overrange of 50 %. The fourth digit is
either a "0" or a "1" so that the instrument is able to give a full -scale readout of 1500 volts with no loss of accuracy.

The meter has four d.c. voltage ranges,
from 1.5 volts to 1000 volts full scale,
plus five resistance ranges, from 1500
ohms to 15 megohms full scale. Ex-

ternal current shunts are available for
current readings.
The accuracy of the instrument is
±0.1% of reading, ±1 digit for d.c.
voltage measurements. Accuracy of resistance measurements is somewhat
lower.
The instrument is rugged, easy to
operate and read, and was designed to
replace conventional analog meters and
panel indicators as well as more expensive digital voltmeters. It is suitable
for production, general test, servicing,
and educational applications.
Using the dual -slope technique (as
described on page 64 of our May, 1967
issue), the Model 7050 combines the
noise- rejection capabilities of integration with the accuracy and stability of
automatic comparison to an internal
standard. Fast response time is assured
by its speed of six measurement samples per second. The meter has an input impedance of greater than 1000
megohms, a floating input which may
be operated 500 volts above ground,
and readout storage providing a non blinking display.

Bird Model 6155 R.F. Wattmeter
For copy of numufacturer's brochure, circle No. 37 on Reader Service Card.
HE Model 6155 is a dual -range ab- axial insertion devices. Modulation may
sorption -type r.f. wattmeter. It is a be monitored across the meter termiportable instrument designed for direct nals or fed to the scope directly from
output power measurements of radio the d.c. jack with meter disconnected
transmitters up to 150 watts from 50( for higher audio signal levels)
When
ohm coaxial transmission lines. It is used in 50 -ohm applications, it has a
intended for general field or laboratory termination v.s.w.r. of less than 1.1:1
service use on c.w., AM, and FM modu- from 2 to 30 MHz.
lation envelopes, but not pulsed modes.
When series (FR current) or tanThe instrument is also useful for line - gential thermal -type devices are used
loss measurement and for checking cofor r.f. power measurement, calibra.

tion adjustments or charts are required
for accuracy. Series devices, when inserted in the line, introduce resistive
and reactive components which disturb
the uniform impedance above the milli watt level. (At signal- generator power
level, a compensating network may be
incorporated to match the line impedance. This is impractical at higher
power because the resistive elements
would become large and cumbersome.)
The major problem encountered with
shunt measurement techniques is the
design of a voltage divider which will
maintain a constant ratio at all r.f. frequencies for which the wattmeter is intended. Basically, there are three types
of shunt dividers: resistive, inductive,
and capacitive.
Of the three, the capacitive divider
is best because it remains purely capacitive over a very wide frequency
range. Since X,. increases as capacitance is reduced, the high values of reactance needed to divide the r.f. line
voltage to less than a volt are easily
obtained with small values of capacitance. However, as frequency is decreased, capacitance must be increased.
The lowest frequency of measurement

finally limits further size reduction, or
vice versa: a physically practical capacitive divider limits power measurement to frequencies above 25 MHz.
An excellent technique for r.f. power
measurement would be a capacitive divider coupled with a current -sensing
loop. It would permit accurate measurement at lower frequencies without
adjustments or references to charts. The
new Bird Termaline® r.f. wattmeter
utilizes this technique. (See diagram.)
A special coupler -detector samples the
r.f. energy from the traveling waves
present in the detector block by both

mutual inductance and capacitance.
The inductive loop length is a small
ELECTRONICS WORLD

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Fraction of a wavelength at the operating frequency, making the loop, for all
practical purposes, a Lumped- constant
L. The capacitive coupling is accomplished with a plate on top of the loop.
This sampling system does not interfere with either line impedance or the

traveling waves and exhibits uniform
response over the frequency range of
the wattmeter. The r.f. energy extracted
by the coupling circuit is rectified, filtered, and displayed on a sensitive
meter calibrated directly in watts, with
a full -scale accuracy of ±5°iß.
The Model 6155 measures power under non -radiating conditions (transmitter output feeding into wattmeter only).

For copy of

METER CABLE

The wattmeter includes a coaxial load
resistor immersed in a dielectric coolant
enclosed within a finned radiator. Fastened to the radiator is the meter housing which may be removed to permit
remote meter readings. The scale is
direct- reading in watts and is expanded at lower levels to increase legibility.
A slide switch on the front face of the
sloped meter case selects either the
0 -50 or 0 -150 watt range.
The r.f. input connector is a patented
"quick- change" female "N" which permits easy interchange with other "QC:'connectors without the use of adapters.
The price of the Model 6155 is $21.5
with une "QC" connector.

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Lafayette 99 -5065 Volt -Ohm -Milliammeter
a tfacturer's brochure, circle No. 38 on Reader Service Card.

1967
Catalog No. 670
512 Pages

IN spite

of the emergence of compact, low -cost digital voltmeters, the
conventional analog-type v.o.m. remains

the most versatile and widely used
piece of test equipment. In those large
numbers of cases where the 2% or
3% accuracy of this type of instrument
is entirely adequate, it is hard to beat
the analog meter, especially where price
is considered.
The new Lafayette Stock No. 995065 "Lab -Tester" v -o -m. is an imported instrument with several unique features. First, it liais the very high ( for
a V.0.m.) input resistance of 100,000
ohms, volt, which means that it has a
higher input resistance than does a con ventional v.t.v.m. on ranges over 100
volts. Second, the meter has a single,
unmarked 24- position selector switch to
change ranges and function. As this
switch is rotated, the range and function of the instrument are "flagged" by
means of a colored marker in one of the
small windows located below each
range- function marking. In this way,
the user can tell what range he is on
without removing his eyes from the
large, 61/2-inch scale meter face.
The switch itself is interesting from
a mechanical point of view. It is a special 4 -pole, 24- position unit with all
its contacts arranged in a straight line.
The wiper is a chain-driven, trolley -like

with Leather
Shoulder Strap

Everything in Electronics
for Home and Industry
from the "World's Hi -Fi
Electronics Center"
LAFAYETTE Radio ELECTRONICS
Dept. RG -7, P. 0. Box 10
Syosset, L. I., N. Y. 11791

1O Send

me the FREE 1967
LAFAYETTE Catalog 670

I
I

RG -7

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Zip

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assembly which moves in a straight
line across the entire width of the meter, carrying the indicator flag with it.
Side -by -side recesses in the switch housing contain individual multiplier and
shunt resistors in a most accessible arrangement.
The meter movement used is a
sensitive 9 -; LA, 135 -mV type with
double -diode overload protection. The
instrument can measure a -c. and d.c.
voltages up to 1000 volts, d.c. current
up to 10 A, and resistance up to 100
megohms.
The instrument case has a stiff carrying handle that can be used to tilt it
up for easy reading. Price is $44.95. A

July, 1967

CIRCLE NO. 112 ON READER SERVICE CARD

PHOTOGRAPHY ANNUAL
selection of the World's finest photographs compiled by the editors of Popular Photography. All
editions $1.25 each:
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Challenges in SST Program
(Continual from page 27)

FROM HiFi STEREO REVIEW

DELUXE
PADDED

conditions, which was standard in the
early days of commercial air transportation, has generally declined but still
remains with us. Systems now ready for
adoption by the airlines enable departures and arrivals under weather conditions which until now were considered
too hazardous for civil transport. A system which allows for safe take -off and
landing under any weather conditions
has not yet been developed. A "hands off" take -off and landing, that is, one
without aid of human control, appears a
desirable goal. This accomplishment requires a complex system that brings together the techniques previously mentioned (autopilot, DIME, CAS) as well
as navigation. The U.S. Navy has already demonstrated that an aircraft can
be landed "hands- off" -a jet fighter has
been successfully brought down aboard
an aircraft carrier without benefit of
guidance by the pilot.

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plus FREE cataloging forms

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Constructed of reinforced fiberboard and covered
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The padded leatherette back (in your color
choice) is gold tooled in an exclusive design
available only on HIFI /STEREO REVIEW Record
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leatherette to keep them looking new after constant use. With each Record and Tape Case you
order you will receive, free of charge,
a specially designed record and tape

Extra

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cataloging form with pressuresensitive backing for affixing to the side of
each case. It enables you to list the
record names and artists and will prove
an invaluable aid in helping you locate
your albums. The catalog form can be
removed from the side of the case at
any time without damaging the leatherette.

Record Cases are available in three sizes: for 7 ",
10" and 12" records. Each case, with a center
divider that separates your records for easy accessibility, holds an average of 20 records in their
original jackets. The Recording Tape Case holds
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The Tape Cases and the 7" Record Cases (with
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My remittance in the amount of $
is enclosed for the Cases indicated below.

Quantity
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Check color choice for back
black only):

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for $19.

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12" Record Case at $3.50 each;

$9; 6 for $17.

Address

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PAYMENT MUST BE ENCLOSED WITH ORDER
_

The problems of air navigation become more prominent as planes cruise
at faster speeds. Less time is permitted
for course changes to avoid storms or
for other reasons. Present weather radars
have a range of approximately 150 miles.
This range must be increased to at least
350 miles for use on the SST. The
weather -radar dome must have low attenuation for transmitted and received
r.f. energy and at the same time must be
capable of withstanding the high temperatures of the aircraft skin. The SST
cruising altitude of 60,000 to 70,000 feet
means that fewer storms will be encountered, just as today's jetliners cruising at 30,000 to 40,000 feet avoid the
lower altitude storms, but weather radar
remains as an important system.
For course navigation, the SST will
borrow the inertial guidance concept
long in use aboard space vehicles. A
redundant system will be employed, providing back -up subsystems if one subsystem fails. More precise fixes of aircraft position will result in operating
economies for the user. Here again,
electronics appears to hold the key to
improved performance.
Two concepts underlie all the ideas
that have been discussed: the notion of
system reliability and system maintainability. Beyond the importance of reliability in insuring the safe conduct of
aircraft operations, there is an economic
implication. If the airlines are to operate
the SST profitably, the availability of
the airplane must be high. "Downtime"
for the SST will mean higher costs to the
carrier than is the case for today's aircraft. Hence, downtime must be minimized. Alaintainability now enters the
picture. The systems must be quickly

repairable and possess the ability to be
maintained with long time intervals between servicings. A self-diagnosing system, one that not only indicates a failure but also points to where the failure
has occurred, is a worthwhile goal. Some
electronic computers already have some
measure of this capability.

Instrumentation System
Related to maintainability is the instrumentation system of the SST. In
addition to the usual instruments for recording flight parameters, a means for
monitoring critical performance characteristics would provide information
useful in maintenance planning. At least
one such system is already in use. Since
March, 1965, Eastern Airlines, Garret AiResearch, and IBM have been operating AIDS (Aircraft Integrated Data
System) Additional airlines, both foreign and domestic, have since placed
.

orders for AIDS.
A step beyond AIDS is AMAS (Airborne Maintenance Analysis System)
The AMAS would not only record data,
as AIDS sloes, but would also transmit
this information in real time for analysis
by a ground station. AMAS could thus
provide a warning to the pilot of impending trouble while the airplane is in
flight. If a serious failure appears imminent, the pilot could land his craft at
the first opportunity, preventing a critical situation.
The piloting of a huge jet aircraft
requires a high degree of skill, particularly during landing and take -off. If the
pilot is not to be overburdened with a
maze of instruments and controls, he
must be supplied with a well -designed
snarl/machine interface. This refers to
the link between the controller and the
controlled. Electronics can lessen the
burden of the pilot's task by providing
instrument displays that are easily read
and hence quickly transmitted to the
mind of the operator. The use of TV
cameras to monitor wheel position during taxi is an example of such a display.
A moving -neap indicator, showing the
aircraft superimposed upon a map of the
local geographic region, can also provide
"quick look" information. Proper layout
of the instrument panel and placement
of controls can also do a great deal to
prevent pilot fatigue and reduce the
possibility of pilot error in operation.
From our discussion, it should be
clear that electronics has much to do
with the planned success of the SST
program. _Many of the problems facing
us are not unique to the SST. The aircraft- airline industry in general will
profit by new developments in electronic systems. The public will benefit by
having rapid, safe, low -cost transportation available. The industry has been
given the challenge, and we have every
reason to believe the challenge will be
met.
.

ELECTRONICS WORLD

www.americanradiohistory.com

Troubleshooting Integrated Circuits
(Continued from page 36)
with D5 and D6 operating as capacitors and R11 and R12.
act as a conventional discriminator. The two -stage audio
preamplifier consists of Q1 and Q12.
13y comparing Figs. 6 and 7, it is immediately apparent
that certain defects can occur in the IC chip itself which will
affect either one of the two sections or, possibly, both. Although the entire IC may have to be replaced, it is still important for the technician to know in which stage the defect
occurs. The reason for this is that a defect in the discriminator transformer, the input transformer, or any of the
external bypass capacitors could cause a loss of output signal.

a,SCR MINA'lR
TRANS.

INPUT
TRANS.

P
4.3MMZ

7. Complete circuit diagram of what is inside IC. The
outboard transformers and bypass capacitors are also shown.

Fig.

INPUT

vSN

the scope, it is assumed that the IC and its associated components are good. Next the volume control and the wiring
to the transistor driver stage would have to be checked. If,
however, the scope does not show a suitable audio signal,
the IC and its associated components must be suspected.
To facilitate troubleshooting, the manufacturer provides
a voltage chart in the service data which requires a v.t.v.m.
and, in some instances, a scope. On terminals 5, 6, and 7,
for example, the scope should show a peak -to -peak voltage
ranging between 4 and 6 volts. RCA points out that improper
bias readings on pins 1, 2, 4, or 5 might be caused by defects
in the input or the discriminator transformer. The manufacturer does not suggest unsoldering the leads of the discriminator transformer to check its resistance because this
would require removing the transformer from its printed circuit mounting, a procedure which is quite involved and
which can easily damage the terminals or printed wiring.

OET %FMR

,-.SVO,T

Fig. 6. Interconnections for the integrated circuit used in set.

It is interesting to see how RCA's troubleshooting instructions are directed towards testing everything else before the
IC itself is tackled. Referring to the block diagram of Fig. 5,
the manufacturer first suggests injecting an audio signal at
the input of the transistor driver stage to make sure that the
transistor section, the output transformer, and the speaker
are all functioning normally. If audio is present at the
speaker, the company recommends injecting a 4.5 -MHz FM
signal at the video detector. A probe is connected to the
audio output terminal, 9, of the IC. If audio can be seen on

AUDIO
AMP.

IMP

MP.

LIMITER

VOLT. REG'

FM OET.

Why not sell the best
DELUXE
ALL -CHANNEL
Part No. 973 -56

3 ZENITH
WAVEMAGNET
INDOOR TV ANTENNAS

Two full -size UHF
loops develop high
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equal to many

outdoor antennas.

built to the quality
standards of Zenith
original parts

ECONOMY
ALL- CHANNEI.
Part No. 973 -55

Zenith has designed these AVavemagnet antennas for sensitive
reception in color or B W. Fully adjustable telescopic dipoles.
Six -position selector switch for top performance on each
channel. Handsome molded hase of high -impact styrene.
Individually packaged for effective sales display.
Order now from your Zenith distrihutor.

VHF ONLY
Part No. 973 -58

,2_,W141211®
he quality goes in before the moue goes oil
7

July, 1967

CIRCLE NO. 95 ON READER SERVICE CARD

www.americanradiohistory.com

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