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(ACCESSION NUMBER) ITHRU)

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4

(NASA CR OR TMX O R AD ~ M B E R I TECHNICAL NOTE NO. 6 Project No. A-588 I

INVESTIGATION OF ELECTRONIC WITCHES FOR ANALOG AND HYBRID COMPUTATION GPO PRICE

OTS PRICE(S) $ $-

By John If. Robertson - Prepared f o r George C . Marshall Space Fl ight Cen Huntsville, Alabama

Contract No, NAS8 -24 73

(Development o f New Methods and Applications of Analog Computation)

31 March 1965

Engineering Experiment Station

GEORGIA INSTITUTE OF Atlanta, Georgia

Iter Microfiche (MF) -2a

TECHNOLOGY 1

https://ntrs.nasa.gov/search.jsp?R=19650015994 2020-04-18T21:14:39+00:00Z

F 0

I

GWRGIA INSTITUTE OF TECHNOLOGY Engineering Experiment S ta t ion

Atlanta, Georgia 30332

1 GIT/EES Report AS88/T6

31 March 1965 1

I N V B T I G A T I O N OF ELECTRONIC SWTCHES

FOR ANALOG AND HYBRID COMPUTATION

BY John FT. Robertson

? r e j e c t Nc. A--;)uu f a 0

Technical Note No, 6

Contract No, NAS8-2b73

(Development of New Methods and Applications of Analog Computation)

For GEDRGE C , IURSHALL SPACE FLIGHT CENTER

Huntsville, A l a b a m a

1 On the basis of a preliminary

were investigated t o determine the

ABSTRACT

l i t e r a t u r e survey, se lec ted analog switches

r e l a t ive performance charac te r i s t ics of ty-pes

considered most promising i n analog o r hybrid computer appl icat ions, Measured

performance parameters a re tabulated and evaluations given f o r examples o f the

modified Guennou chopper, the nomaturating two- and f our-transistor switches,

the complementary t r a n s i s t o r bridge, t he series-shunt unifet switch, and the six-

diode bridge gate, a l l constructed from avai lable standard semiconductor compo.- nents.

six-diode bridge gate and with the series-shunt f i e ld -e f f ec t - t r ans i s to r switch t o ~

From these resu l t s , it is recommended t h a t fu r the r work be done with the

optimize t h e i r performance f o r spec i f ic analog and hybrid computer functions.

FOREWJRD

Contract lJAs8-2473 was in i t i a t ed i n September 1961 and has covered a va r i e ty

of assignments r e l a t ing t o work a t t he F l igh t Simulation Branch of Marshall Space

F l ight Center's Computation Laboratory,

been D r . W. K. Pols torff (R-COMP-RS).

gram is now being provided by personnel of t he Georgia Tech School of E lec t r i ca l

Engineering in the general areas of ( a ) nonstationary noise s tudies , and (b) e r r o r

analysis f o r hybrid computation. However, t he laboratory invest igat ions described

herein were performed by M r . John W. Robertson, with technical guidance from Mr. Frank R. Williamson, Jr., in the Special Problems Branch of the Engineering Exper- iment S t a t i o n t s Physical Sciences Division, under which the project has thus f a r

been administered. It is planned t h a t these invest igat ions w i l l be continued on

The PBFC Project Technical Off icer has

A large portion of the e f fo r t on t h i s pro-

a more l imited bas is during the remainder of the current

ing in December 1965. contract period, t e m i n a t -

F. Dixon Pro jec t Director A 4 8 8

ii

I .

CONTENTS

. I . I N T R O D U C T I O N . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

I1 . DESCRIPTION OF SWITCH TYPES STUDIED . . . . . . . . . . . . . . . . 3 2.1 . Modified Guennou Chopper . . . . . . . . . . . . . . . . . . 3 2.2. Nonsaturating Transistor Switches . . . . . . . . . . . . . . 4 2.3. Complementary Transistor Bridge . . . . . . . . . . . . . . . 5’ 2-4 . Series-Shunt Unifet Switch . . . . . . . . . . . . . . . . . 6 2-5. SixtDiode Bridge Gate . . . . . . . . . . . . . . . . . . . . 7

I11 . SWITCH MODEL DEFINITIONS AND PERKIRMANCE CRITERIA . . . . . . . . 8 3.1 . Idea l and Nonideal Switch Models . . . . . . . . . . . . . . 8 3-2 . Switch Perfomance Parameters . . . . . . . . . . . . . . . . 9 3-3 . Model Performance Parameters . . . . . . . . . . . . . . . . 10 3-4 . Parameter Calculations f o r Specif ic Ci rcu i t s . . . . . . . . 11

I V . EXPERIMENTAL RESULTS AND DISCUSSION . . . . . . . . . . . . . . . . 13 4.1 . Performance Data Summary . . . . . . . . . . . . . . . . . . 13 4.2 . The Modified Guennou Chopper . . . . . . . . . . . . . . . . 15 4-3. The Nonsaturating Transistor Switches . . . . . . . . . . . . 16 4-4. The Complementary Transistor Bridge . . . . . . . . . . . . . 1 7 4-5’. The S e r i e s S h u n t a S w i t c h . . . . . . . . . . . . . . . . . 18 b-6 . The Six-Diode Bridge Gate . . . . . . . . . . . . . . . . . . 19

V . CONCLUSIONS AND RECOMMENDATIONS 21

5.1 . Summary Evaluation . . . . . . . . . . . . . . . . . . . . . 2 1 5-2 . Future Work . . . . . . . . . . . . . . . . . . . . . . . . . _ _ 73

Appendix -BIBLIOGRAPHY . . . . . . . . . . . . . . . . . . . . . . . . 23 A . Transis tor Gate References . . . . . . . . . . . . . . . . . 24 B . Diode Gate References . . . . . . . . . . . . . . . . . . . . 25’ C. FET Gate References . . . . . . . . . . . . . . . . . . . . . 26 D . Miscellaneous Gate References . . . . . . . . . . . . . . . . 26 E . Supplementary References . . . . . . . . . . . . . . . . . . 2 7

iii

I - INTRODUCTION

The general aim of the work on which t h i s report i s based is t o obtain a design f o r an analog switch of improved performance.

Analog switching devices, both electromechanical and electronic , are used I n communications, they a re var ious ly referred i n many f i e l d s of e lectronics .

t o a s commutators, multiplexers, modulators o r demodulators, and gates.

analog computation, switching devices may be cal led choppers, modulators,

samplers, sampling switches, input selectors , or simply switches. Other f i e l d s

a l s o have a variety of technical names f o r analog switches, each with i t s own special ized meaning, However, the basic function of a l l of the devices is really

the same, and the d i f f e ren t terminologies tend t o indicate not s o much the nature of a device as i t s mode of operation or appl icat ion, Thus, some applications may

a l l o w use of devices that a re res t r ic ted t o a pa r t i cu la r frequency of operation, while others may require t h a t the device be capable o f more o r less random opera- t i on ,

eit.her lnssless t ransmission o r coxplete a t tenuat ion cf an k p u t sigfial, xhen

and as desired.

I n

But i n e i t h e r case the fundamental objective i s t o provide, a l te rna te ly ,

Typical examples of analog and hybrid computer applications o f switches a re (1) sampling switches f o r sample-and-hold c i r cu i t s , (2) reset switches i n

mode control logic, and ( 3 ) r e se t -pu l se generator switches f o r incremental analog-to-digital conversion devices.'' Such appl icat ions require switches

capable of switching a t in te rva ls ranging from i n f i n i t y (continuous operation)

t o possibly microseconds, with nonsymmetrical on and off times.

successive on and o f f times need t o be inde-pendent.

I n addition,

For a switch t o meet the above requirements, it m u s t be capable o f continu-

ous operation.

ture , including the majority of switches with ac-coupled drives. f o r computer appl icat ion must a l s o have dc-coupled s igna l channels.

types of switches, such as the diode ring-bridge modulator and t h e diode capaci- tance modulator a r e inherently incapable of continuous operation, Other types,

such as the t rans is tor ized switch of W i l l i a m s , have ac-coupled s igna l channels,

This i n i tself rules out many of the p o s s i b i l i t i e s i n ths l i t e r a -

Analog switches Several

' t A s i n the "AID Converterr1 developed by F. R. Williamson, Jr. under Contract DA-01-009 om-853 and subsequently incorporated i n a generalized analog in t eg ra to r ( rlEGII1) under the present NASA contract ,

-1-

I v

Several switches having ac-coupled drive signals, such as the Bright c i r cu i t ,

may be modified t o provide continuous operation through the use of a s i l i c o n

controlled switch (SCS) and a bias source, and would be expected t o give the same perfonnance as the unmodified versions,

Other desirable q u a l i t i e s in an analog switch a r e economy, r e l i a b i l i t y ,

high switching speed, and high frequency capab i l i t i e s .

known performance, the modified units mentioned above a r e more complex and

l imited i n switching speed. Photoconductive gates also f a l l i n t o the slow switching speed category with presently avai lable dr ives ( l a s e r diodes excluded).

cated above are ident i f ied and described i n the next chapter,

Besides yielding already

The switching c i r c u i t s chosen f o r fu r the r inves t iga t ion on the bases ind i -

-2 -

I1 - DESCRIPTION OF SWITCH TYPES STUDIED

2-1. Modified Guennou Chopper (see References A13,A18)

The Guennou chopper i s a simple two-transistor switching c i r cu i t , designed by S. Guennou i n France and subsequently described by H. Kemhadjian i n the April

1960 issue of Mullard Technical Communications (Reference A 1 3 ) . version shown below was arrived a t by removing the coupling capaci tor of the

standard chopper and direct-coupling the load,

The modified

Current drive is supplied t o the base of each t rans is tor a t the value resu l t - ing i n lowest inverse-mode saturat ion voltage V

the base resistors Ft,l and Rb2. The load resis tance F$ should be large enough s o as not t o load the balance potentiometer R, which i n tu rn i s chosen so as t o make

the e f f e c t s of Rin i n s e r i e s with the pot negl igible . The t r a n s i s t o r s a re opera- ted i n the inverse mode i n order t o provide a low offset voltage, and they should

be matched against one another f o r inverse-mode current gain p emi t t e r leakage current I

( s a t . ) CE iJ achieved by adjust ing

-.

collector-to- i' and sa tura t ion voltage VcE( sat. ) i. CED iJ

r---- I

1 I ----

>

>RL >

Figure 1. Modified Guennou Chopper.

-3 -

I .

2-2. Nonsaturating Transistor Switches (see Reference As’)

The nonsaturating t r a n s i s t o r switch is a type of switched complementary

H i s V.wo-transistorIf version is similar emitter-follower c i r c u i t ,

gested by Brubaker i n Reference 85, but omi ts the first emitter-f o l l m r stage (Q3,Qb).

t o ground and releasing the bases of the f irst complementary emitter-follower

(c,d) . Transis tors f o r each emitter-follower should be a complementary pair, matched f o r normal-mode current gain (p ) and having a high current gain a t the temperatures of operation.

Shown below is the Itfour-transistor11 design sug-

Voltage dr ive i s supplied t o points a and b, thus a l t e rna te ly short ing

n

Figure 2. Four-Transistor Nonsaturating Switch.

-4 -

r

2-3. Complementary Transistor Bridge (see Reference A l 2 )

Depicted below is the t r ans i s to r bridge c i r c u i t described by Kalfaian

i n Reference A 1 2 f o r low-level switching applications. This has been pre-

viously referred t o on t h i s project as the llcornplementary microvolt transistor bridge, ' 1

Complementary dr ive s ignals are applied a t points a and b t o t u r n a l l t r a n s i s t o r s o f f o r on a t the same time.

o f f o u r t rans is tors , two npn and two pnp types, matched for normal-mode current gain pn, collector-to-emitter leakage current Icm, and sa tura t ion resis tance

RCE(sat.) over the temperature range of i n t e r e s t ,

This c i r c u i t requires a matched set

--

I I

Rs

I 1

--1

-

/ Figure 3. Complementary Trans i s to r Bridge,

-5-

2-4. Series-Shunt Unifet Switch (see Reference C3)

The simple switching c i r c u i t shown below u t i l i z e s a p a i r of unipolar f i e l d - e f f e c t t r a n s i s t o r s (FET's) , a and b serve t o t u r n on one FET and simultaneously t u r n off the other.

are no matching requirements f o r t h i s c i r c u i t ,

Push-pull dr ive s igna ls applied a t points

There

Figure 4. Series-Shunt Unifet Switch.

-6-

2-5. Six-Diode Bridge Gate (see Reference B7) -- Lc

In an excel lent 1955 paper (Reference B7), Millman and Puckett analyzed

the performance of low-level gating c i r c u i t s incorporating two, fou r , o r six diode uni t s i n a bridge-type configuration, six-diode version would be most sui table f o r fu r the r invest igat ion under the

present project .

Their r e su l t s indicated t h a t the

I n the c i r c u i t as shown below, push-pull control voltages are applied a t

points a and b and cause the f o u r bridge diodes simultaneously t o e i t h e r conduct o r block,

qui te accurately balanced, the f o u r bridge diodes should have a high r a t i o of

forward conductance t o reverse leakage, and the two output diodes should be

c lose ly matched as regards t h e i r leakage currents ,

For optimal performance, the fixed supply voltages (4 V) need t o be

I +v

y e s I CR6 (RC I I - . i'

Figure 5 . Six-Diode Bridge Gate.

-7-

I11 - SWITCH MODEL DEFINITIONS AND PERFORMANCE CRITERIA

3-1. Idea l and Nonideal Switch Models

Ideally, a switching device should exhib i t zero on-resistance, i n f i n i t e

off-resistance, t o t a l absence o f e i t h e r o f f s e t voltage o r dr ive leakage, and infinite operating speed (zero actuat ion time), O f course, no real switch can

provide pe r fec t ly idea l performance. a l ike are l imited i n operating speed, have some o f f s e t voltage, have l e s s than

i n f i n i t e off-resistance, and more than zero on-resistance. I n addition, they

a re not completely isolated f rom ground, and e l e c t r i c a l l y actuated types w i l l

possess some dr ive leakage, leakage, have been repEsented i n the switch equivalent-circui t diagrams below,

Alternat ive models a re of course possible (e ,g . , see Reference A 1 7 ) .

Electronic and electromechanical switches

These nonideal properties, except f o r the dr ive

.t '

Figure 6. SFST Switch Ncdels:

P - ---I (a> L--

Figure 7. SPDT Switch Models:

(a) actual , (b) ideal,

--1 r--

--_I ( b)

(a) actual, (b) i dea l .

-8-

3-2. Switch Performance Parameters

*Eout A v b ) = E.

In

After some consideration, it was decided t h a t the electronic switches t o be studied should be t rea ted as amplifiers, with gain and offset measurements

made on them under both flonfl and IloffII conditions, were a l so t o be determined, and additional data would be taken if deemed neces-

s a ry o r desirable ~

are shown i n equation and diagrammatic form below.

Switching frequency l i m i t s

Definit ions of the primary performance parameters measured

o r ig ina l ly a Tek- t ron ix 545, l a t e r a Keithley 610A, then a John Fluke 823A

switch on

I i r----

vo = I Switch on

I Ein Ov

LD = I Switch off

- Switch on l - Ein - Ov

ip 4 I 7 7

same as above

sarre as abcve

same as above

Figure 8. Switch Parameter Measurement Ci rcu i t s .

-9-

.

3-3, Model Performance Parameters

As a matter of general in te res t , the ac tua l switch performance parameters defined above may be expressed i n terms of the theo re t i ca l switch models pre-

sented under Section 3-1. af te r eliminating t e rns of negligible magnitude i n accordance with the assump- t i o n s noted,

The following approximate relat ionships are obtained

AV( on) t

V: 0

SPST Model

R L

% + R 2

SPDT Model

LD:

Conditions : R*<%<-=Rp R3 RS<& 1’ R 4

R e R R R <a1 3 S 1 9 3

e . s;zL1 e >>L (R /R ) i n i n 1 1 3

-10-

3-4. Performance Calculations f o r Specific Switches

Although the foregoing mathematical expressions and the models from which

they are derived can provide useful ins ights i n to switch behavior, they a re not of much help i n attempting t o predict the performance of an a c t u a l switch. One

may, however, obtain quant i ta t ive estimates of desired performance parameters i n any given case by fa i r ly straightforward analysis of the switch c i r cu i t ry . Pre-

sented hereunder are results derived f o r the two most important switch types

considered.

Series-Shunt Unifet Switch

Given IGss = gate-to-source leakage current o f FET,

= drain-to-source resistance with z e r o gate-to-drain voltage, rd s (drain-to-source voltage)/(pirichkoff dra in cukrent), Roff

then f o r the c i r c u i t shown i n Section 2-4, provided % i s small compared t o r ds 2 fo l l aws :

(Q ) and Roff (Q2), the switch performance parameters may be calculated as

Iz, Av(off) = rds(Q2)

rds(Q2) + Roff(Q1'

Six-Diode Bridge Gate

Analysis of the switch given in Section 2-5 is f a c i l i t a t e d by use of the

diode equivalent c i r u c i t shown below (containing an assumed i d e a l diode).

Figure 9 . Equivalent Circuit f o r Diode.

Any o f f se t voltage Vo i n the six-diode gate can normally be balanced out

by adjust ing potentiometer R . This adjustment w i l l t yp ica l ly provide compensa-

t i o n f o r values of R i n the bridge output diodes i n the ra t io of 3 ~ 1 (with f

-11-

I .

I -

The dr ive leakage L of the six-diode gate can be assumed t o be produced D s o l e l y by the difference i n leakage currents of the two output diodes.

assumption w i l l be va l id under the conditions tha t t he bridge output diodes

have back resis tance (%) large compared t o the load resis tance ( %), t ha t the two dr ive diodes have small forward resis tance (R ), and t h a t the impedance of

the dr ive source i s small.

This

f

Values f o r on voltage gain and off voltage gain of the six-diode gate may

be calculated qui te readi ly with formulas derived from an ac model of tk c i r cu i t - - o r , with considerably more calculations, from a de analysis (see Reference B 7 ) . The approximate expressions f o r predicting switch performance a re thus as follows.

= 0 (adjusted); vO

Rc/2 RL Rc/2 t. Rf/2 + R/4 'T-5 , Av(on) =

-12-

I V - MPERIME3JTA.L RESULTS AND DISCUSSION

k-1. Performance Data Summarv

Performance data are tabulated hereunder f o r t he various e lec t ronic switches

t h a t have been constructed and tes ted on t h i s project .

f i e d i n the t ab le as follows:

The switches are ident i -

MGC- modified Guennou chopper 4TNS- f our- t ransis tor nonsaturating switch 2T NS - two -trans ist o r nonsaturating switch

SSUS- series-shunt unifet switch CTB- complementary t r ans i s to r bridge

6DG/F- six-diode bridge gate using Fairchild 1N3595's 6DG/G- six-diode bridge gate using G.E. 1N4443's

The tab le includes values f o r the main performance parameters defined i n Section 3-2, namely:

gain, LV(off); and drive leakage, I,D, I n the case of t he series-shunt unifet

switch and the two six-diode gates, these parameters were determined not only

a t the normal room temperature of 2 5 O C but a l so a t an oven-controlled tempera-

t u r e of 50°C.

t u re s e n s i t i v i t i e s AV /AT and ALD/AT, as shown i n the t a b l e ,

mined by taking the reciprocal of the summed rise and f a l l times ( L e , , times

req~ l rc : ! fcr th5 cutpc-t ~ c l t ~ g e t..n reach i t s final value, r i s i n g and f a l l i n g ) o f the switching waveform as observed on an oscilloscope. suffers somewhat i n accuracy due t o the necessi ty of determining a point a t

which the waveform may be said t o have reached i ts final value.

more accurate, procedure might be desirable f o r some appl icat icns .

on voltage gain, kV(on); offset voltage, lo; o f f voltage

The t w o sets of data then yielded values f o r the nominal tempera-

----o- The column designated LX gives the m a x i m u m frequency of operation deter-

Obviously, t h i s method

A di f fe ren t ,

The e n t r i e s marked E. represent maximum s igna l input l eve l s permitted -in f o r the pa r t i cu la r c i r c u i t components used,

limits but do indicate what might be considered appropriate levels of operation

f o r each type of switch tes ted ,

These a re not l i s t e d as ultimate

A s a f i n a l point of in terest , it should be mentioned t h a t the first four

switch models l i s t e d were b u i l t on standard phenolic assemply boards, with no

spec ia l precautions f o r shielding.

hand, were enclosed i n small aluminum boxes and were connected t o the dr ive c i r c u i t r y by shielded cables , The method of construction f o r these models may

be seen from the photographs below, one of which a l s o shows a typ ica l arrange-

ment of the instrumentation involved i n a switch performance test .

The last three switch models, on the other

-13 -

0.120

0,800 24 27.2

0,001

0.020 18 0.75

)le 1. EXPERIMENTAL VALUES 1 IF SWTCH PERFORMANCE PARAMETERS. -.-

A

3 + 1

+ 5

I

Switch -3.-

0.2 I .6x10-1 MGC 0.69 60

50 hTNS 0.81 0.2 I . 8 ~ 1 0 ' ~

2TNS 1 7 I 50 + 5 0.72

0.9 0.1 I CTB

ssm-25" 0.95 0.040 I .5xlOW4 0.040 I 0.040 350

0.040 1 -50"

6DG/F-25*

-50"

0.989

0,990 2.5 420

+20

I- 6D G/G-2sd

-50"

0.989

0.988 2.5

V given a s zero, indicating tha t c i r cu i t permits adjusting t o zero f o r any par t icular temperature a d pair' of supply voltages (balanced within 1%) 0

I

Figure 10. Shielded Construction of Six- Diode Gate.

Figure 11. Switch Performance Tests.

Arrangement o f Instrumentation f o r

h-2. The Modified Guennou Choumr

The Guennou chopper, i n its modified form, offers l i t t l e benef i t over a

The small improvement afforded l i e s simple s ingle- t ransis tor shunt chopper, i n making the offset voltage and drive leakage more nearly equal, and thus

easing the compensation problem s l igh t ly .

A number of d i f f e ren t t r ans i s to r types were t r i e d i n the Guennou c i r cu i t , The types t e s t ed included but none provided any r e a l l y outstanding advantage,

2 N 2 2 0 , 2 N k O u , 2 N 6 9 7 , 2 N 7 0 6 , 2 N 1 1 3 2 , 2 N 1 1 7 9 , 2 N 1 6 0 5 A Y 2 N 2 1 0 2 , and 2 N 2 6 1 3 , Ref - erence A 1 8 points up the need f o r t r ans i s to r s with inverse current gains (pi) on the order of 10. are avai lable with high inverse current gains. However, from the basic capa-

b i l i t i e s of the Guennou c i r cu i t , it is doubtful whether the construction of

fu r the r switches of t h i s type could be ju s t i f i ed . Even if the transistors were

replaced by idea l switches, the r a t i o of the on voltage gain t o the o f f voltage

gain (a suggested f igure of merit) would not be g rea t ly enhanced,

Special switching t r ans i s to r s , both s i l i c o n and germanium,

-15-

4-3. The Nonsaturating Transis tor Switches -- - I -

The two- and f our-transistor nonsaturating switches suggested by Brubaker (Reference A S ) gave much be t t e r resu l t s than the Guennou chopper.

o f t h i s switch employed pa i rs of complementary t r ans i s to r s (2N697, 2Nll32) matched

t o within 10% f o r pn, RCE(sat.), and ICm on a Tektronix 575 t r a n s i s t o r curve

t r ace r .

avai lable . o f matched pairs of t r ans i s to r s ( o r matched quadruples) purchased from the manu-

fac turer . a matched p a i r and mounted i n the same can, should provide even b e t t e r performance

by reducing temperature differences between t r ans i s to r s i n the same stage of the

switch.

Construction

This was the bes t match possible with the l imited number of t r ans i s to r s

Performance of the switch could undoubtedly be improved by the use

Dual t rans is tors , consisting of one npn and one pnp each drawn f rom

It i s doubtful, however, whether the off voltage gain can be reduced g rea t ly with the bases of t he switch transistors being switched t o ground a s a t present,

An arrangement whereby the bases of a l l of these t r a n s i s t o r s could be switched

t o sone b ias voltage, s o as t o provide reverse bias t o the switch t rans is tors ,

would probably reduce the o f f voltage gain by a t least one order of magnitude,

The magnitude of the input voltage i s l imited by the avai lable supply vol t - age and the limited heat diss ipat ion of the t r ans i s to r s . The supply voltage may be increased up t o the limit of the transistor ratings, provided s teps a re taken t o insure that the t r a n s i s t o r d i ss ipa t ion remains within limits,

This switch suffers generally from the requiremerrts f o r matched, high-gain, low-leakage transistors, and balanced power-supply voltages.

supply voltages w i l l be ref lected as an o f f se t i n the output voltage, a s w i l l

any mismatch of the switching transistors. output voltage t o remove the offset i s accomplished by adjust ing the b i a s current of the switch-

ing transistors, i n supply voltage and hence the shor t - t e rm s t a b i l i t y requirements can become ra the r acute ,

Unbalance of the

Adjustment of the

This offset adjustment is usable only f o r long-term var ia t ions

-16-

‘4-4, Complementary Transis tor Bridge

Construction o f the complementary t r ans i s to r bridge u t i l i z e d a matched

quadruple of t rans is tors , two npn (2N697) and two pnp (2Nll32). Matching o f

the uni ts was f o r pn, RCE(sat.) and Icm, and was accomplished t o within 10% by means of a Tektronix 575 t r ans i s to r curve t r ace r .

possible with the available t rans is tors , sistors would probably resul t in l o w e r offset voltage, lower o f f voltage gain,

and lower dr ive leakage. matched quadruple of transistors mounted i n a s ingle To-5 enclosure,

by t r a n s i s t o r breakdown and can be increased by using higher-voltage t r a n s i s t o r s ,”

Another f ac to r l imi t ing the input signal m a x i m u m is the insu la t ion of t he b ias

supply f o r the bridge and the supplies f o r t he dr ive c i r cu i t ry ,

This was the best match

Better matching and low leakage tran-

Temperature e f f e c t s could be minimized by using a

The maximum input voltage t o t h i s switch ( i n our case, 4 30 vo l t s ) was s e t

The lack o f any requirement f o r balanced voltages by the bridge i tself

causes the unbalance s e n s i t i v i t y t o be zero . r~ l a t . iw ly l i t t l e effect ,

numbe r of pawe r supplie s required ,

Variations i n the b i a s supply have However, a major disadvantage of t h i s switch is the

2L

” Note t h a t it is e a s i e r t o match t ransis tors of the same type, and that higher voltage ra t ings a re avai lable with s i l i c o n t r a n s i s t o r s of the npn va r i e ty than with the pnp ty-pe. sistors, but a t the cost of a higher degree of complexity i n the dr ive c i r c u i t r y (Reference A 1 2 ) .

Thus, a bridge might be constructed using a l l npn t ran-

-17-

4-5'. Series-Shunt Unifet Switch

The series-shunt unipolar f i e ld -e f f ec t t rans is tor switch reported on was

constructed from a Si l iconix telemetry designer 's k i t . The FET uni ts involved

( types 2N3380 and 2N3386), although giving good resu l t s , can be impruved upon. Desirable propert ies include low drain cutoff current I (o f f ) , low gate-to-

low drain-to-source resis tance r source leakage current IGss, to -d ra in voltage), and low gate-to-channd capacitance CGss.

of the FETs during the on time fo r each,

the leakages of the control diodes CR

of the FETs Q, and Q2 themselves, o r other means,

is required. signal with no i n t r i n s i c offset voltage,

signal levels and gate-to-channel breakdown, I n experimenting with t h i s switch, shcielding w a s found necessary f o r t he

D ( a t zero gate- d s

Note t h a t some means must be provided t o discharge the gate capacitance This may be accomplished by u t i l i z i n g

and CR2, the gate-channel diode leakages 1

No matching of components is necessary i n t h i s switch, and no supply voltage

The f i e l d e f f e c t t r ans i s to r presents a pure resis tance t o t he

Input voltage is l imited by the dr ive

f irst time-at least partly because of the long l i n e s required t o allow opera- t i o n inside the oven f o r high temperature measurements.

were thus taken with approximately s i x feet of RG-62/U between the output of the

gate and the load.

observe the output,

Frequency measurements

A Tektronix 545A with 47 pf shunt capacitance was used t o

The absence of a power supply requirement i n the FET switch is a major

advantage. This feature materially reduces the amount of auxiliary equipment

needed f o r the switch, and a t the same time the output contains no components due t o power-supply var ia t ions o r unbalance, Temperature var ia t ions have l i t t l e

effect on the gate offset voltage and dr ive leakage, of t he c i r c u i t should provide great ly increased r e l i a b i l i t y and lower cost .

Linearity of the ser'ies-shunt un i fe t switch was roughly checked i n the

course of the laboratory tests by applying a sine-wave input t o the switch and observing i ts output while driven a t a high switching r a t e ,

w a s v i s ib le i n the chopped output s ine wave,

l i n e a r i t y would of course be desirable i n any subsequent evaluation of improved

FET switches,

The inherent s impl ic i ty

No d i s to r t ion

A more accurate measurement o f

-18-

4-6. Six-Diode Bridge Gate

The six-diode gate gave the lowest value of off voltage gain of any c i r c u i t

t es ted .

General Elec t r ic lN4.443 diodes,

poor r e su l t s .

found t o be out o f tolerance in leakage current.

the remaining avai lable diodes were t e s t ed t o ascer ta in t h e i r adherence t o the

published parameter limits. tolerance, only two s l i g h t l y out of tolerance on forward drop a t one value of current.

was decided t o u t i l i z e the fou r good 1N3595's as the bridge diodes i n one c i r c u i t , and 1N4443' s as the drive diodes f o r both c i r c u i t s ,

Switch uni t s were constructed using Fairchi ld type 1N3595 diodes and

The i n i t i a l unit using 1N3595 diodes gave very

When the diodes were removed from the bridge and tested, a l l were A s a r e s u l t of this discovery,

Only four lN3595 diodes were found t o be within

A l l of the 1Nh43ts were within tolerance f o r leakage current and It

It was a l s o decided t o use the leakage current values measured a t the v o l t - ages specif ied i n the data i n an attempt t o provide matched diode pairs f o r the input and output legs of the bridge, This, i n e f fec t , neglected the various

phenomena such as surface leakage which cause the leakage currents of diodes t o

- 1 3 . depart from the values predicted by the diode equation: I 0 I [e -e V/KTX S

Subsequent measurements indicated that, i n t h i s case, the other e f f e c t s predomi-

nate ,

Matching of the reverse leakage, of the output diodes par t icu lar ly , a t the

ac tua l voltage t o be used i s necessary f o r best r e su l t s .

high forward conductance a re desirable i n the bridge.

contr ibutes far less t o the over-al l gate of fse t voltage,

c i r c u i t used, the dr ive diodes were calculated t o produce about 1 microvolt of

offset voltage f o r each 40 nanoamperes difference i n leakage current between the t w o ,

Low-leakage diodes with

The drive diodes' leakage

I n the pa r t i cu la r

Contributions t o the gate offset voltage by unbalance of the supply vol t -

ages i n the on state require extremely s t r ingent regulation of the supply voltages

t o ensure t h a t t he unbalance remains small enough t o introduce no s igni f icant

e r r o r ,

necessary regulation of the supplies was calculated t o be .00015%. With the

a c t u a l gates constructed, s e n s i t i v i t y o f t h e output voltage t o supply unbalance

was observed t o be approximately 5 millivolts f o r each vol t o f unbalance.

I n order t o l i m i t t h i s output e f f e c t t o a 1 microvolt contribution, the

Formulas presented i n Section 3 4 enable LD, Av(on), and Av(off) f o r the six-diode gate t o be predicted f r o m measured cha rac t e r i s t i c s of t he individual

diodes, In general, such theore t ica l calculations agreed well with experimental

-19-

results f o r the ac tua l gates constructed, which were designed t o operate a t a 20-volt signal level .

f o r a gate designed t o operate a t a 1-volt s igna l leve l . ance was found t o be considerably poorer i n t h i s case,

l a rges t r a t io s of maximum input s igna l t o dr ive leakage, and likewise the smallest v a 1 - i ~ ~ of o f f voltage gain, w i l l be obtained by using the highest pract icable

supply and drive voltages.

The formulas were also used t o calculate the performance

The predicted perform- Indications are t h a t the

Switching speed could be considerably improved by connecting a second six- diode gate s o as t o switch t o ground the output of the f irst gate during the

time t h a t it i s nonconducting,

Although no attempt was made to balance out gate dr ive leakage during the

invest igat ions described herein, it i s probable t h a t such compensation could be provided f o r i n the case of the six-diode bridge c i r c u i t ,

-20-

V - CONCLUSIONS AND RECOMMENDATIONS

5-1. Summary Evaluation

The Guennou chopper, i n its modified form, o f f e r s l i t t l e improvement over

a simple s ingle- t ransis tor shunt chopper, dr ive leakage, which is lower than f o r the shunt chopper, and the lack of a

supply voltage, var ia t ions of which could a f f e c t the output,

o f improving the performance grea t ly appears qu i te small,

The advantages afforded l i e i n the

The p o s s i b i l i t y

Advantages o f the four- t ransis tor nonsaturating switch are few, except t h a t it w i l l give b e t t e r performance than the Guennou chopper o r a simple shunt

t r a n s i s t o r chopper,

with provision f o r back-biasing the t r a n s i s t o r bases which are now switched t o ground.

operation, a l s o should improve performance,

A fu r the r reduction i n Av(off) by a f a c t o r of

D u a l t r ans i s to r s i n one enclosure, matched over a temperature range of

i s probable

The complementary t r a n s i s t o r bridge offers improved performance over t h e

Major advantages of t h i s c i r c u i t are the increase i n four- t ransis tor switch, maximum s igna l voltage which can be applied without damaging the components,

and the r e l a t ive immunity t o power supply var ia t ions. possible u t i l i z i n g ultra-low-leakage t rans is tors , matched over a temperature

range,

some improvement.

Improvements should be

Dual- and quad-transistors mounted i n a s ingle can might also of fe r

The c i r c u i t offering the most advantages o f any t r i e d thus far is the

series-shunt FET switch. No matched components are necessary, no supply vo l t -

age var ia t ions can affect the output, no adjustments a re necessary t o the out-

put voltage. the six-diode bridge,

use of FET's with lower r

Finally, t h i s c i r cu i t gave l o w e r Av(off) than any other except Improvements t o t h i s c i r c u i t may be possible through the

and MOS FETfs with much lower gate leakage, ds

The six-diode bridge had the highest r a t i o of Av(on) t o Av(off) o f any Few other advantages are c i r c u i t tes ted, due t o the extremely low Av(off) .

offered by t h i s c i r cu i t , however, in t h i s c i r c u i t ' s performance i s very small a t the present time.

the highest r a t i o of forward t o reverse current known t o us were used, and several years w i l l probably be required f o r production diodes with s ign i f i can t ly b e t t e r

r a t i o s of forward t o reverse current t o reach the market.

The probabi l i ty of s ign i f i can t improvements Diodes having

-21-

5-2. Future Work

It i s recommended t h a t fur ther invest igat ive e f f o r t be applied t o the FFT

switches, control led switches (SCS' s) i n the approximate configuration of t h e complementary

t r a n s i s t o r bridge be constructed and t e s t e d ,

would demonstrate the improvement possible with the bes t ava i lab le unipolar and

MOS ty-pe FET' s. on and o f f per iods approaching in f in i ty , thus allowing ac csupling of the dr ive

s igna l without l imi t ing the lower frequency of operation of t he switch.

It i s a l s o recommended tha t a bridge c i r c u i t incorporating s i l i c o n

The construct ion o f the FET switches

The SCS bridge would permit use o f very narrow drive pulses f o r

-22 -

I .

4

Appendix - BIBLIOGRAPHY

I n i t i a l e f f o r t s on t h i s program were applied t o a study of the per t inent

l i t e r a t u r e on electronic switching techniques and applications. The l i t e r a t u r e

survey has included a review of The Ehgineering Index since 1961 and continuing

coverage of t he D E Technical Abstract Bul le t in f r o m the January 1963 issue on,

I n addition, several of the major e lec t ronic engineering journals are regular ly

received and scanned, as are new-product announcements and data shee ts from a

number of manufacturers in the semiconductor components f i e ld .

The bibliography presented herein contains 72 e n t r i e s divided in to the

following subject categories--(the number of documents c i t ed i n each category is shown in parentheses):

A. Transis tor Gate References (25) B. Diode Gate References (9)

C. Fl3T Gate References (11) D. Miscellaneous Gate References (18)

Bidirectional T rans i s to r Gates (1) Hall Generator Gates (1) Photo Gates (6) Varicap Gates (1) Integrated Tube Gates ( 2 ) Vacuum Tube Gates ( 2 ) &?.Tickle Oxide Gate (1) Thyristor Gates (3)

E. Supplementary References (9)

The E l a t i v e importance o f various references t o the invest igat ions reported

herein i s indicated by a s t e r i sks in the margin.

primary reference--one which provided e s s e n t i a l o r valuable information f o r a

pa r t i cu la r switch under study.

one which served t o supplement a primary reference o r which provided information

permitt ing the elimination of cer ta in switches from fu r the r study,

A double a s t e r i s k denotes a

A s ingle a s t e r i s k denotes a secondary reference--

-23-

Bibliography

A . Transis tor Gate References

Amperex Electronic Corp. : llTypes 2N2569/2N2570 S i l i con Planar/Epitaxial Transistors. Application Note, pp. 4-6, July 1963.

Baker, R. H., R. E. McMahan, and R. G , Burgess, "The Diamond Circuit,Il MIT Lincoln Laboratory Report on Contract AF 19(628)500, 30 January 1963. AD-400 955.

Bright, R. L., IIJunction Transistors Used as Switches, I t Transactions of the AIEE, vol. 74, Par t I (Communications and Electronics), pp. 111-121, March 1955.

Amplifiers, Electronics, pp. 135-137, Apr i l 195s'.

Instrumentation and Computers, randum No, 78, May 1963. N63-23058.

National Convention Record, vol. 5, par t 5, pp. 57-60, March 1957.

and Perfom.ance of the SPAT as a Transis tor Chopper," Instrument Practice, vol. 17, no, 4, pp. 387-399, Apr i l 1963.

Application Note, February 1963,

Indus t r ies and Tele-Tech, pp. 42-43, 108-111, December 1956,

Bright, R. L. , and A . P. Kruper, ttTransistor Choppers f o r Stable D.C .

Brubaker, T. A . , "A Nonsaturating Transis tor Switch f o r Analog/Hybrid University of Arizona, A , C . L. Memo-

Dorsett , E., and J. H. Searcy, IILow Level Electronic Switch,Il IRE

Ekiss, J. A., and J. W. Halligan, "The Application, Characterisation,

Hughes Semiconductor Division, ItTransistor Choppers Application,

Hurley, R. B., IITransistorized Low Level Chopper-Circuits, lr Electronic

3tAlO- Hutcheon, I. C., and D. Summers, "A Low-Drift Transis tor tihopperdTy-pe D.C. Amplifier with High Gain and Large Dynamic Range,

1960. * A l l - Jackson9 T. B., tlEvaluation o f NOLC 15-Channel Transistorized Electronic

Commutator, 11 Naval Ordnance Laboratory (Corona, Calif, ), 2spoz-t NOLC/410, N&VORD 5919, April 1958.

p. 60, 3 January 1961r.

by S. Guennou i n French), Mullard Technical Communications, vol. 5, no. 43, Apr i l 1960,

Proceedin s of the I n s t i t u t i o n of Elec t r ica l Engineers, Paper No, 32 + 7 M , March

AD-208 448. 3 ~ e A 1 2 - Kalfaian, M. V., IITransistor Bridge Switches Microvolts, I t Electronics,

w $ A l 3 - Kemhadjian, H., "D.C. Amplifier with Balanced Chopper1! (based on report

A a - Kruper, A . P. , Vwitching Transistors Used as a Subst i tute f o r Mechani- c a l Low-Level Choppers,l! Transactions of t he AIEE, vol. (Communications and Electronics 1, pp. Ul-l44, March 19%.

74, Pa r t I

++AlS- Rasch, P. J., YSome Aspects of Transis tor Demodulators, MIT Instrumenta- t i o n Laboratory, Report on Contract AF Ob( 647) 303, 38' pages, February 1962. AD-607 745.

++Al6- Rees, J. W., flApplicability o f Transis tors as Low-Lek1 Signal Switches, Army Missile Command (Redstone Arsenal), Report RG TR63-16, l.4 August 1963. AD-419 213.

-24 -

Roy, R., IrTransistorized High Frequency Chopper Design, I! Electronic Design, vol. 7, no. 16, pp. 41-44, 6 August 1958.

Simpson, J. H., IITemperature Effects i n Low-Level Transis tor Choppers, I1

Solid S t a t e Design, pp. 22-28, March 1964,

Smith, A. B., IITransistor Switches f o r Low-Level Signals, Electro- Technology, vol, 69, no. 2, pp. 202-204, February 1962.

Solbakken, A., "Design o f High-Speed Electronic Switches, 11 MIT Electronics Systems Laboratory, Report on D , S, R, Project 8823, January 1963.

Texas Instruments, Inc, , !!Transistor Choppers, Application Note, Septem- ber 1959.

Walter, J. M., and J. H. Searcy, !!A Law Level Electronic Subcommutator, I t

IRE Transactions of Professional Group on Telemetry and Remote Control, paper 3.2, 1957.

Weber, H. J., flDeveloping a High-Low Level Telemetering Gate, Automatic Control, vol. 17, no. 5, pp. 21-23, December 1962.

W i l l i a m s , A. J., J. U. Eyllm. and N. E. P o l s t e r , fISome Advances i n Transis tor Modulators f o r Precise Measurement,lf Proceedings o f the National Electronics Conference> vol. 13, pp. 40-54, 1957.

Laboratory ( m i t e Oak, Md , ) , Report NOL TR62 -139, November 1962, AD-291 696.

Williams, K. G., !!A Transistorized Electronic Switch, I! Naval Ordnance

B. Diode Gate References

B1-

B2 - ?cB3-

?F.B4-

ttB5-

B6-

-WtB7 - +tB8-

B9-

Belevitch, V., "Linear Theory o f Bridge and Ring Modulation Circuits,If

Bems, K. L. , and B. E. Bishop, "High Speed Multiplexing with Closed-

E lec t r i ca l Communications, V o l . 25, pp. 62-73, 1948.

Ring Counters,lt Electronics, vol. 32, pp. 48-50, 26 June 1959.

-

Ettinger, G. M., IITransistor Modulator f o r F l igh t Trainer, Electronics, pp. 126-127, September 1955.

Keonjian, E. J., and J, E. Schmidt, Wing-N3dKiator Reads Low-Level D.C.,!! Electronic Industr ies , vol. 17, pp. 86-89, Apr i l 195'8.

Kharchenko, R. R., and V. N. Malinovskii, "Diode Switching Ci rcu i t s f o r Measuring Purposes, 11 Measurement Techniques (English t r ans l a t ion of Izmer i te l~naya Teknika) no, 8, pp. 626 -633, A u g u s t 1961.

Manley, 0 . P., !!Investigation and Evaluation of an Electronic Gate, 11

Naval Ordnance Laboratory (White Oak, Md.), Report NAVORD 4335, February 1957. A D - a l 505.

Gates,!! Proceedings of the IRE, vol. 43, pp. 29-37, January 1955.

Sens i t i v i ty f o r Use i n Junction Transis tor Direct-Current Amplifiers, Proceedings o f the National Electronics Conference, vol. 11, pp. l&l-454, 1955.

Millman, J. , and T , H , Puckett, flAccurate Linear Bidirect ional Diode

Moody, N. F., "A S i l icon Junction Diode Modulator o f 10 A m p e r e -8

Moody, N. F., Wil icon Diode Ring Modulation, Military Standardization Handbook: June 1960,

Selected Semiconductor Circuits, MIL-HDBK-215, pp. 2-25, -26,

-25-

c1-

c2-

I ,r ,043- ,,

+tcL - c5-

c7-

C8-

c9-

i - C . FET Gate References

Cope, R. W., Y3emiconductors Improve Box-Car Circui ts , I t Electronic Design, pp. 106-106, 16 March 19&.

Electronic Equipment Engineering Staff , IIFET: F i r s t User Survey, 11

Electronic Equipment Engineering, pp, 88-97, January 1964, Fa t ta l , L. , "Field-Effect Transistors as Choppers, Semiconductor Products, pp. 13-18, Appil' 19a.

Gulbenk, J., and T. F. Prosser, IIHow Modules Make Complex Design Simple,Il Electronics, vol. 37, no, 32, pp, 50-54, 28 December 19&.

Hindson, W. D., and T . Nishiaaki, "FET Makes High Level Phase Sensi- tive Detector, Electronic Design, pp, 80-81, 25 October 1963.

Martin, T. B., V i r c u i t Applications of the Field-Effect-Transistor- Par t I, Semiconductor Products, pp. 33-39, February 1962,

Martin, T . B. , Wircu i t Applications of the Field-Effect Transistor-- P a r t 11, Semiconductor Products, pp. 30-38, March 1962.

Rose, J. A , , Potpourri of FET Applications, E lec t r i ca l Design News, vol. 10, no. 3, pp. 3845, March 1965.

Shipley, M. "FET Low-Level Choppers, Electronic Equipment Engineering, pp. 63-65, February 1964.

Shipley, M., IIAnalog Switching Circuits use Field-Effect Devices, I1

Electronics, vol. 37, no, 32, pp. 45-51, 28 December 19&.

-

'211- Siliconix, Inc, , "Field-Effect Low-Level Choppers, Application Note, F i le 103, November 1963.

D. Miscellaneous Gate References

Bidirect ional T r a n s i s t o r Gates

D 1 - Trousdale, R. B., IfGermanium B i l a t e r a l Switching Transistors, Texas Ins t rmen t s9 Inc., Application Note, March 1961.

H a l l Generator Gates

D2- Marcus, T . J., !%Highly Sensit ive Electronic Chopper, Electronics, pp. 66-68, 2 October 1959.

Photo Gates

++D3- Bonin, E. L., "Light-Coupled Semiconductor Switch f o r Low-Level Multi-

+CD4 = Steward, R. D., flA Signal Processing Photoconductive Switching Device, I t

plexing," Electronics, vol. 38, no. 3, pp. 54-59, 8 February 1956.

Proceedings of the National Electronics Conference, v o l . 17, pp. 360- 368, 1961.

D5- Texas Instruments, Inc, , "The Photo-Duo-Diode: Theory, Measurement of Parameters, and Operation, Application Note, Apr i l 1961.

D6- Texas Instruments, Inc, , W l i c o n Planar Photo Device LS-LOO, I t Applica- t i o n Note SC-3323-1262, December 1962,

-26-

D 7 - Texas Instruments, Inc., IISilicon Photo-Voltaic Light Sensor, I f Appli-

D 8 - Texas Instruments, Inc., Vwitching Character is t ics of t he S i l icon cat ion Note SC-3580-263, February 1963,

Planar Phototransistor,If Technical Information Bullet in SC-3932.

Varicap Gates I

~

D9- Hurtig, C , R., YSerniconductor-Capacitor Chopper, Military Standardiza- t i o n Handbook: Selected Semiconductor Circui ts , MIL, HDBK-215, pp. 2-27, -28, -29, June lm,

- Integrated Ci rcu i t Gates

-:5D10- Bell, B., and B, Mitchell, "The INCH-Discussion and Applications, Solid S t a t e Design, vol. 3, no, 10, pp. 34-42, October 1962,

Design News, vol. 10, no. 1, pp. 20-35, January 1965, D 1 1 - Libaw, W. H., IINondigital Application of Microcircuits, E lec t r i ca l

- % D E - Sandlin, I!. C., Wptoelectronics Today, I f Elec t r i ca l Design News, vo l . 10, no. 1, pp. 72-87, January 1965.

Vacuum Tube Gates

D 1 3 - Goldstein, L. P., Vwo Electronic Analog t o D ig i t a l Converters, Danish Atomic Energy Commission, Report RR 80, February 19&, AD-446 694.

D a - Nisson, C . J. , tlAn Analog Triode-Diode Function Generator, I t Johns Hopkins University, Bumble Bee Report 318, 88 pages, May 1963. A D 4 2 1 555.

Nickle Oxide Gate

D 1 5 - Beadle, FT. E,, "A Thin-Film, Nickle Oxide Switch," Stanford Electronics Labs, Report SEL 63 075, 40 pages, August 1963. ADA21-935.

Thyristor Gates

D16- Gentry, F, E., R. I. Scace, and J. F. Esson, "The Development and Evalua- t ion o f a B i l a t e ra l Triode Switch,ll General Elec t r ic Company, Quar t e r ly Progress Report 1 on Contract NObsr 91151, 46 pages, July 19&.

Control Engineering, vol. 11, no. 3 , pp. 75-76, March 1964.

Control Engineering, vol. 11, no. 4, pp. 69-72, Apr i l 1964.

AD-603 560.

D l 7 - Southworth, M. P., IIBidirectional S t a t i c Switch Simplif ies AC Control, I t

D 1 8 - Southworth, M. P.? "The Threshold Switch-New Component f o r AC Control,

E. Supplementary References

E l - Blake, R. F., W a t i c Relays--How Well Do They Work--How Can You Use

+E2- Dahlman, P. O. , "Electronic Switching f o r Communication Systems, IBM Them, Aerospace Electronics, pp. a3-153, July 1960.

Federal Systems Division, Report TR-023-027 on Contract AF 3O( 602) 2600, 26 March 1963. AD-299 220.

vol. 9, no. 7, pp. 49-62, 29 March 1961. -:$E31 Electronic Design Staff, IIElectronic Commutators, Electronic Design,

-2 7-

I i -

4- I -

. E5-

E6-

E7-

E8 ..

E9 -

Kinney, M., llSemiconductor Switching Annotated Bibliography, I t Autonetics December 1961. AD-284 712.

and Multiplexing:, A P a r t i a l l y Report EM-7590, 27 pages, 4

Kranzler, M. M., Wommutators f o r Airborne Multiplex Telemetering, 1'

Electronics, v o l . 32, pp. 46-47, 3 July 1959. Military Standardization Handbook: Selected Semiconductor Circuits,

!Modulators, MIL-HDBK-215, pp. 2-9, -10, -11, June 1960. Opp, F., and J. A . Walston, fY3emiconductor Choppers, Texas Instru- ments, Inc., Application Report, October 1959.

Roitman, M. S., S. A . Gofman, L. P. Olomutskii, and A . N. Karmadonov, "Zero S t a b i l i t y of Synchronous Detectors with Semiconductor Diodes and Triodes, n a p Teknika) no, 9, pp. 718-722, September 1961.

Searcy, J. H. WADC TRS6-178, February 1956.

E lec t r i ca l Measurements ( b g l i s h t r ans l a t ion o f Izmeritell

Y5urvey o f Low Level Modulators, I t Radiation, Inc. Report PB-121 385.

-28-