NBS SPECIAL PUBLICATION 400-41

U.S. DEPARTMENT OF COMMERCE / National Bureau of Standards

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Semiconductor Measurement Technology:

A Versatile

High-Voltage Bias Supply for

Extended Range MIS

C(V) and G(V) Measurements
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=" Located at Boulder, Colorado 80302.
Semiconductor Measurement Technology:

A Versatile High-Voltage Bias Supply for

Extended Range MIS C(V) and G(V) Measurements

Paul Kuczer, Harvey O. Hook, and

Alvin M. Goodman

RCA Laboratories

Princeton, New Jersey 08540

This activity was supported by

The Defense Advanced Research Projects Agency

and The National Bureau of Standards

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Dr. Sidney Harman, Under Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Annbler, Acting Director

Issued December 1977
Library of Congress Cataloging in Publication Data

Kuczer, Paul A versatile high-voltage bias supply for extended range MIS C(V) and G(V) measurements. (Semiconductor measurement technology) (NBS special publication ; 400^1)

Supt. of Docs, no.: CI 3. 10:400^1

1. Metal insulator semiconductors—Testing. 2. Electric meters- Power supply. 3. Electric capacity. 4. Electric conductivity. 5. High

voltages. I. Hook, Harvey O., joint author. II. Goodman, Alvin M.,

joint author. III. Title. IV. Series. V. Series: United States. National Bureau of Standards. Special publication ; 400^1. QC100.U57 no. 400-41 [TK7871.99.M4] 602Ms [621.3815'2] 77-25245

National Bureau of Standards Special Publication 400-41

Nat. Bur. Stand. (U.S.), Spec. Publ. 400-41,69 pages (Dec. 1977) CODEN: XNBSAV

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1977

For sale by the Superintendent of Documents, U.S. Government Printing OlSce, Washington, B.C. 20402

Price S2. 40—Stock No. 003-003-01869-4

j!r U.S. GOVERNMENT PRINTING OFFICE : 1977 O—26 1 -07

1
TABLE OF CONTENTS

PAGE

1. Introduction 1

2. General Description of Equipment, Operation and Performance 2

2.1. Control Module 2

2.2. High-Voltage Amplifier Module 6

3. Circuit Details of Control Module 7 3.1. Sweep Time Selection 18

3.2. Up/Down Counter and Comparator 19

3.3. Sweep Function Selection 21

3.4. Sweep Command Circuit 21

a. Command Pushbutton Switches and Associated

Circuitry 21

b. Direction Circuit 23

c. Sweep Status Indicators 23

d. Pen Control Circuit 24

e. Continuous Restart Circuit 24

3.5. Analog Circuit 24

3.6. Power Supplies and Metering 25

4. Circuit Details of High-Voltage Amplifier Module 25

4.1. General Specifications 25

4.2. Output Stage 25

4.3. Driver Circuit 32

5. Calibration and Adjustments 32

5.1. Bias Supply Control Module 32

a. Digital Circuit 32

b. Analog Circuit 32

5.2. High-Voltage Amplifier Module 34

a. Zero-Offset Adjustment 34

b. Quiescent Point Adjustment 35

iii
TABLE OF CONTENTS (Continued)

PAGE

ACKNOWLEDGMENT 35

APPENDICES

A. Bias Supply Control Module 37

B. High-Voltage Amplifier Module 47

REFERENCES 61

FIGURE CAPTIONS

Figure 1. Control module front panel 2

Figure 2, Sweep function waveforms 4

Figure 3. Control module rear panel 5

Figure 4. High-voltage amplifier module front panel 8

Figure 5. High-voltage amplifier module rear panel 8

Figure 6. Functional block diagram of high-voltage bias

supply 9

Figure 7. Sweep time selection circuit 10

Figure 8. Up/down counter and comparator circuit 11

Figure 9. Sweep function selection circuit 12

Figure 10. Sweep command circuit 13

Figure 11. Analog circuit 14

Figure 12. Counter number sequences for the six sweep

functions (single sweep) 20

Figure 13. Power supplies and metering for bias supply control

module 26

Figure 14. Power supplies and switching for high-voltage

amplifier module 27

Figure 15. High-voltage amplifier schematic 28

Figure MAI. Front panel, bias supply control module 38

iv
FIGURE CAPTIONS (Continued)

PAGE

Figure iyiA2. Rear panel, bias supply control module 39

Figure MAS. Base panel and power supply clamps, bias

supply control module 40

Figure MA4. Digital logic board layout, bias supply control

module 41

Figure MA5. Analog circuit board component side, bias supply

control module 42

Figure MA6. Cables WlOl, W105, and crystal circuit subassembly,

bias supply control module 43

Figure MA7. Analog printed-circuit board, bias supply control

module 44

Figure Al. Top view of bias supply control module with top cover removed 45

Figure A2. Top view of analog circuit board, bias supply

control module 46

Figure MBl. Front panel, HV amplifier module 48

Figure MB2. Rear panel, HV amplifier module 49

Figure MB3. Ease panel, HV amplifier module 50

Figure MB4. Side panels, HV amplifier module ^1

Figure MBS. Chassis top and bottom covers, HV amplifier

module

Figure MB6. HV connector assembly, HV amplifier module ....

Figure MB7. Driver printed-circuit board, HV amplifier module . -54

Figure MBS. HV amplifier printed-circuit board, HV amplifier

module

Figure MB9. Printed-circuit board and potting container, HV

amplifier module

Figure MBIO. Driver board, HV amplifier module

Figure MBll. Clamp for power supply PS 203

V
FIGURE CAPTIONS (Continued)

PAGE

Figure Bl. Top view of HV amplifier module with top cover removed 58

Figure B2, Top view of HV amplifier board 59

Figure B3. Bottom view of HV amplifier module with bottom

cover removed 60

-

, ' LIST OF TABLES

Table 1. Electrical Parts List for Bias Supply Control Module . 15

Table 2. Truth Table for UP/DOWN Comparator 19

Table 3. Conditions Required for the Termination of a Single

Sweep 22

Table 4. Electrical Parts List for HV Amplifier Module .... 29

Table 5. List of Mechanical Parts in Bias Supply Control Module

(not commercially available) 37

Table 6. List of Mechanical Parts in High-Voltage Amplifier

Module (not commercially available) 47

vi
PREFACE

This study was carried out at the RCA Laboratories as a part of the

Semiconductor Technology Program in the Electronic Technology Division

at the National Bureau of Standards. The Semiconductor Technology Program serves to focus NBS efforts to enhance the performance, interchangeability, and reliability of discrete semiconductor devices and

integrated circuits through improvements in measurement technology for use in specifying materials and devices in national and international

commerce and for use by industry in controlling device fabrication

processes. The work was supported by the Defense Advanced Research

Projects Agency* through the National Bureau of Standards' Semiconductor

Technology Program, Contract 5-35912. The contract was monitored by

R. L. Raybold as the Contracting Officer's Technical Representative

(COTR) and R. Y. Koyama as Assistant COTR.

DISCLAIMER

Certain commercial equipment, instruments, or materials are identified

in this report in order to adequately specify the experimental procedure. In no case does such identification imply recommendation or en- dorsement by the National Bureau of Standards, nor does it imply that

the material or equipment identified is necessarily the best available

for the purpose.

Larger scale drawings of the mechanical parts and full-scale negatives

of the custom circuit boards are available on request from the COTR,

Tech-A-361, National Bureau of Standards, Washington, DC 20234.

^Through ARPA Order 2397, Program Code 6D10.

vii

SEMICONDUCTOR MEASUREMENT TECHNOLOGY: A Versatile High-Voltage

Bias Supply for Extended Range MIS C(V) and G(V) Measurements

by

Paul Kuczer, Harvey 0. Hook, and Alvin M. Goodman

RCA Laboratories

Princeton, N.J. 08540

Abstract : Recently developed technology has enabled the measurement of MIS C(V) and G(V)* at bias-voltage magnitudes as large as

25 kV. This report describes a versatile high-voltage power supply

intended for use as a bias source in carrying out such measurements.

The design allows the user a wide variety of options in the selection

of the sweep function (waveform), sweep time, initial bias voltage, and

the amplitude of the bias sweep. There are six possible sweep functions: (i) increasing ramp, (ii) decreasing ramp, (iii) positive

polarity half-wave sawtooth (increasing ramp followed by decreasing

ramp), (iv) negative polarity half-wave sawtooth (decreasing

ramp followed by increasing ramp), (v) full-wave sawtooth starting

with increasing ramp, and (vi) full-wave sawtooth starting with

decreasing ramp. Either single or repetitive sweeps may be selected.

The sweep time from the initial value to the end of the first ramp

segment may be varied from 1 to 2000 s. Operator convenience is

enhanced by certain features of the design; among these are lightemitting diodes which display the state of the sweep and automatic

pen control if the sweep is used with an x-y recorder.

Key Words: High-voltage bias supply; high-voltage C (V) and G(V)

measurements; high-voltage function generator; high-voltage sweep;

semiconductor devices; silicon-on-sapphire measurements.

1. INTRODUCTION

A recently developed modification of the MIS C(V) measurement technique [1] has extended its useful range, allowing it to be used for

the measurement of samples with insulating layers more than two orders

of magnitude greater in thickness than was previously possible. This

use, however, often requires the application of a very large bias

voltage to the capacitor sample being measured. In the first highvoltage MIS C(V) measurements of Al-sapphire-Si capacitors [2], the

bias voltage was controlled manually and an attempt was made to keep

the rate of change of bias as uniform as possible. It was clear, however, that the measured capacitance, C, depended to some extent upon

the rate of change of the bias voltage, V, and that manual control of

*The following abbreviations are used: MIS for metal- insulatorsemiconductor ; C (V) for capacitance as a function of voltage; G(V)

for conductance as a function of voltage.

1
the bias voltage would be unsatisfactory for general use. Since the

extended-range modification of the measurement technique was relatively new, and there existed very little experience on which to base

a set of requirements for a suitable bias supply, we decided to design

and construct an extremely versatile supply that would lend itself to

a variety of possible future applications. The bias supply which re- sulted from that work is described in this report. It was intended

for use with other equipment developed concurrently and described in

references 3-5.

2. GENERAL DESCRIPTION OF EQUIPMENT, OPERATION, AND PERFORMANCE

The high-voltage bias supply is constructed in the form of two modules: (1) a control module with digital logic, a D/A (digital to

analog) converter, and amplifiers to provide the required waveforms at

low- and medium-voltage levels, and (2) a high-voltage amplifier module

(HVAM)

.

2.1 Control Module

The control module is designed to allow the user a wide variety of

options in the selection of the (1) sweep function (waveform), (2)

sweep time, (3) initial bias voltage, and (4) amplitude of the

bias sweep. The front panel of the control module (illustrated in

fig. 1) shows the location of all of the user-operated controls.

Figure 1. Control module front panel.

2
Operating power for the digital logic and low-voltage analog circuitryis controlled by the switch marked LOGIC* located above the POWER

label. The function of the two adjacent switches will be discussed

later.

Any one of six basic sweep functions may be selected by depressing (to

its latched position) the appropriate pushbutton under the heading

SWEEP FUNCTION. Each sweep function is composed of one or more "ramp"

segments. The term ramp is understood here to mean a voltage which

varies linearly with time.

The time, T, required for the sweep is controlled by selection of the

INITIAL TO PEAK SWEEP TIME; i.e., the time required for the sweep

voltage to change from its initial value to the first maximum excursion from that initial value.

If a single sweep is desired the CONT. -SINGLE pushbutton under the

COMMAND heading should be in the released (out) position. If continuous operation is desired, this pushbutton should be in the

depressed (in) position.

The magnitude of the starting value of the sweep is set by adjusting

the INITIAL OFFSET control and the adjacent TRIM control. The polarity of the initial offset voltage is selected by setting the adjacent

three-position toggle switch to the appropriate + or - position or to

ZERO if no initial offset is desired.

The maximum one-way excursion of the sweep voltage from its initial

value is set by adjusting the SWEEP AMPLITUDE control and the adjacent

TRIM control.

Before initiating a sweep, the digital control circuits must be reset

by momentarily depressing the RESET pushbutton. The sweep may then be

initiated by depressing the GO pushbutton. The resulting sweep voltage as a function of time will be one of the waveforms shown in

figure 2. If the sweep has been started in the continuous operation

mode, the sweep will continue indefinitely until it Is ended in one of

two ways: (1) the continuous sweep may be ended by depressing the

RESET pushbutton; this will bring the sweep voltage back to its initial

value almost instantaneously, i.e., at slewing speed. (2) Alternatively, the continuous sweep may be ended by releasing the CONT.-

SINGLE pushbutton to its out position. This causes a reversion to

single sweep operation, which ends with the completion of the sweep

function then in progress.

The sweep may be stopped at any time by pressing the pushbutton marked

HOLD. The output voltage will then remain constant until the GO, RETURN or RESET pushbutton is pressed. If the GO pushbutton is pressed,

*Words corresponding to labels, callouts, or titles in the figures

are capitalized in the text.

3
SWEEP

FUNCTION

Figure 2. Sweep function waveforms.

4
the sweep will continue from the point at which it had been stopped.

If the RETURN pushbutton is pressed the sweep voltage will return to

the initial value by the shortest possible path (single ramp) at a sweep rate corresponding to the selected SWEEP AMPLITUDE and INITIAL

TO PEAK SWEEP TIME. If the RESET pushbutton is pressed, the sweep

voltage will return to its initial value almost instantaneously, i.e.,

at slewing speed.

The operating state of the sweep is indicated by four monitor lights

(light-emitting diodes) located under the label SWEEP. The UP or DOWN light will be on if the sweep is on an up or down ramp, respectively. The HOLD light indicates that the sweep has been stopped by

pressing the HOLD pushbutton. The END light indicates completion of

a sweep. The absence of any light indicates that the RESET pushbutton has been pressed.

The sweep waveforms generated in the control module are available from

connectors on the rear panel (see fig. 3) at three different voltage

levels. The nominal low voltage output of the control module has a maximum magnitude of about 10 V with respect to ground. The output

is "antisymmetric" with respect to ground. That is, the voltages

which appear at the two output terminals (BNC connectors labeled

+10 V and -10 V) have equal magnitudes but are of opposite polarity

with respect to ground. Thus, when one terminal is at +10 V, the

other is at -10 V and the total output magnitude is 20 V. The

voltage at each output terminal is also bipolar; i.e., it can have

Figure 3. Control module rear panel.

5
either polarity with respect to ground. When the +10 V terminal

is positive with respect to ground, the output polarity is said to

be positive or normal; if the +10 V terminal is negative with respect

to ground, the output polarity is said to be negative or reversed.

This total voltage is indicated on the digital voltmeter when the

METER RANGE switch is in the 20-V position.

There are two additional outputs available from the control module,

(1) A single-ended output proportional to the previously described

bipolar output, but equal to one-half of its magnitude. This voltage

appears at a single BNC connector labeled ANALOG OUTPUT and is intended

for use with grounded instruments to monitor the bipolar output. (2) A

medium level bipolar output equal to ten times the low-voltage bipolar

output. This voltage appears at two terminals (UHF connectors) labeled

+100 V and -100 V. The total voltage between these terminals is indicated on the digital voltmeter when the METER RANGE switch is in the

200-V position. Operating power for this medium level analog circuitry

is controlled by the switch marked 200 V located above the POWER label.

A BNC connector (labeled PEN) located on the rear panel provides a connection to the contacts of a pen-control relay. When the AUTO PEN

switch on the front panel is in the ENABLE position, the pen relay is

energized during sweep operation; this provides a closed circuit at

the PEN connector. If the AUTO PEN switch is in the DISABLE position

the relay cannot be energized and the PEN control circuit remains open.

The operating power for the digital logic and all levels of analog circuitry is provided through the connector labeled AC POWER INPUT.

The operating power for the high-voltage amplifier module is provided

through the connector labeled TO HV POWER INPUT and is controlled by

the switch marked HV located above the POWER label. This connector

also provides a circuit connection between the control and high-voltage

modules that may be used for monitoring the voltage level (attenuated

1000:1) at the output of the HV amplifier module. This voltage may be

read on the digital voltmeter of the control module when the METER

RANGE switch is in the HV position.

There is an unlabeled connector in the rear panel of the control module. It was originally intended for interfacing digital logic signals

in the control module with a data acquisition system for extendedrange MIS C(V) measurements. This system has not yet been developed

and the connector is, at present, unused.

2.2 High-Voltage Amplifier Module

The high-voltage amplifier module (HVAM) is designed to accept the

nominal low-voltage bipolar output of the control module at its input,

and to produce a high-voltage bipolar output at levels up to "^25 kV

C'^12.5 kV between each output terminal and ground). The front and

6
rear panels are shown in figures 4 and 5, respectively. The input

terminals are located on the rear panel and labeled +10 V DRIVE and

-10 V DRIVE. The output terminals are located on the front panel and

are labeled + and -.

The gain of the HVAM is controlled by a switch located on the front

panel and labeled HIGH VOLTAGE RANGE (kV) . There are five positions

of this switch, +1, +2.5, +5, +10, +25 each indicating the nominal maximum output voltage magnitude in kilovolts corresponding to that switch

position with the maximum nominal input voltage. The corresponding

amplifier gain figures are 50, 125, 250, 500, and 1250.

Operating power is supplied through a connector labeled POWER INPUT

and located on the rear panel. The operating power is controlled by

the switch on the control module labeled HV. This switch has three

positions. The OFF position indicates that all power to the HVAM is

shut off. The STANDBY position indicates that power is connected to

all of the low-voltage control circuitry, the regulator tube heaters,

and a time-delay relay, but not to the plate supplies for the regulator tubes. The regulator tube plate supplies are powered only when

the time-delay ('^8 s) relay has closed. High voltage can reach the

output terminals only if the time-delay relay has closed, the HV switch

is in the ON position, and the safety interlock circuit [4] is complete.

The latter occurs when a low resistance is connected across the insulated BNC connector marked SAFETY INTERLOCK.

Three pilot lights on the front panel of the HVAM and one on the front

panel of the control module monitor the status of operating power for

the HVAM. When the HV switch is in the OFF position, all pilot lights

should be off. When the HV switch is in the STANDBY position, the

pilot light above the HV switch and the one marked CONTROL POWER

should be on. The pilot light marked STANDBY will be on only after

the time-delay relay has closed. When the HV switch is in the ON

position, the OUTPUT pilot light on the HVAM will be on if the safety

Interlock circuit is complete. Note that it is possible for the OUTPUT light to be on when the STANDBY light is off during the ^8 s waiting period of the time-delay relay; there will be no voltage at

the output terminals during this time.

3. CIRCUIT DETAILS OF CONTROL MODULE

A functional block diagram of both modules of the high-voltage bias

supply is shown in figure 6. This section deals with the circuits

comprising the control module portion of that figure. These circuits

are described in five schematic diagrams, one for each of the blocks

in the digital portion (figs. 7 to 10) and a fifth (fig. 11) for the

three blocks representing the analog portion. The circuit elements

shown in these figures are described in table 1.

In brief, a crystal -oscillator-derived square wave (clock) is fed to an up/down counter producing a binary number which varies linearly

7
HIGH VOLTAGE

CONTROL POWER STANDBY OUTPUT

Figure 4. High-voltage amplifier module front panel.

SAFETY

INTERLOCK

Figure 5. High-voltage amplifier module rear panel.

8
r RESET

SWEEP COMMAND

CIRCUIT

UJt

_j

CD<

z

Hi

END OF^ SWEEP

NORMAL DIRECTION

NORMAL DIRECTION

A>B

RUNNING DIRECTION

SWEEP TIME

SELECTION

CLOCK

HV AMPLIFIER MODULE

± 25 KV OUT

SWEEP FUNCTION

SELECTION

X m < II <

UP/DOWN COUNTER

AND COMPARATOR

12 BIT D/A

CONVERTER

—r-

±20V OUT

±200V0UT

ZDo

a

D

O

O

o

o

<

<

_CqNTRqL _MODJJLE_ j

Figure 6, Functional block diagram of high-voltage bias supply.

9
10
11
lT: ct? Q

A

• A

AAA . CO <x>

1 —

6 O 6 o 6 O 6 o

•HO

•Ha

c

o

•H

•Uo

<u rH

dJ

CDS

O

•HU

o

c

(U

0)

IS

•H

PC4

CNJ I rO I

12
13

Table 1. Electrical Parts List for Bias Supply Control Module

Schematic Reference

AR A, AR B, AR D, AR F

AR C

AR E

AR G, AR H

B

C

D

E

F

G

H

I

J

K

L

M

N

0

P

Q

R

S

T

U

V

W

X

Y

ZAA

BB

CC

DD

EE

FF

ClOl

C102, C103

C104

C105

C106

Description (Commercial description, ''^ if appropriate, shown in parentheses)

General purpose FET operational amplifier.

(Teledyne Philbrick, Type 1421).

Digital to analog converter (Analog Devices, Type AD562 KD/BIN)

Precision instrumentation amplifier

(Analog Devices Type AD 521)

High-voltage FET operational amplifier

(Teledyne Philbrick, Type 1022).

CD4011AE

CD4068AE

CD4011AE

MC14522

MC14522

MC14522

CD4049AE

CD4013AE

CD4068AE

CD4024AE

CD4019AE

Dual-In-line, 10 kfi resistor network

[contains 15 resistors; 12 used in

circuit, figure 7],

MC14522

CD4011AE

CD4025AE

CD4013AE

CD4023AE

CD4029AE

CD4029AE

CD4029AE

CD4049AE

CD4013AE

CD4013AE

CD4001AE

CD4063AE

CD4063AE

CD4063AE

12 V Relay SPST [RLlOl]

CD4013AE

CD4013AE

CD4017AE

0.22 yF, 50 V, mylar capacitor

0.1 ]iF , 50 V, mylar capacitor

0.047 yF, 25 V, ceramic capacitor

100 pF, silvered mica capacitor

200 pF, silvered mica capacitor

*See disclaimer on p. vii.

15
Table 1. (Continued)

Schematic Reference

C107, C108, C109, ) Clio, cm, C112, C113 f C114, C115, C116, C117

C118, C119

DlOl, D102, D103, D104

D105

DSlOl

DS102

DS103

FlOl, F102

F103

JlOl

J102

J103

J104

J105, J106

J107, J108, J109

JllO, Jill ^ J112, J113

MlOl

PlOl

P102, P103

PSIOI

PS102

PS103

RlOl, R102

R103

R104, R105, R106, R107

R108

RIO 9

RllO, Rill, R112, R113, R114

R115, R116, R117

R118

R119

*See disclaimer on p. vii.

Description (Commercial description,*

if appropriate, shown in parentheses)

1.5 yF, 50 V, ceramic capacitor

200 pF, silvered mica capacitor

22 yF, 15 V, tantalum capacitor

Light-Emitting Diode (Hewlett-Packard 4655)

IN914

Panel lamp, neon, clear

(Leecraft type 44N-0117)

Panel lamp, neon, amber

(Leecraft type 44N-0113)

Panel lamp, neon, red

(Leecraft type 44N-0111)

1/4 A. SB, 3 AG Type

2A. SB, 3 AG Type

22/44 PCB connector 0.156 contact

centers (Amphenol 225-22221-101)

35/70 PCB connector 0.100 contact centers

(Stanford Applied Engineering CPH 7000-70)

"Jones" plug (Cinch P-308-AB)

15/30 PCB connector 0.156 contact centers

(Amphenol 225-21521-101)

16-pin dual-in-line socket

Insulated BNC chassis connector

UHF chassis connector

"Grabber" clip (Pomona Electronics

Type 3925)

4 1/2 digit panel meter (Ballantine 8310-05)

16-pin dual-in-line plug

8-pin cable male connector, "Jones" type

(Cinch Type P308-CCT)

Power supply, regulated with 14 V (3 0.5A

(Power One Type HA15-5)

Power supply, regulated with +15 V and

-15 V outputs (3 10 mA (Acopian type D15-10A)

Power supply, regulated with +120 V and

-120 V outputs @ 40 mA (Teledyne-Philbrick

type 2217)

10 k^^, 5%, 1/2 W

22 m, 5%, 1/4 W

910 5%, 1/2 W

162 fi, 1%, 1/2 W

30.1 kn, 1%, 1/2 W

100 kfi, 1%, 1/2 W

50 k^^, 1/2 W

33 kfi, 1/2 W

16
Schematic Reference

R120, R121

R122, R123

R125

, R128, R129, R130, R131

, R132, R134, R135

, R137

R140

R126

R12 7 R124

R136

R138

R133

R139

R141

R142

R152

RLlOl

SlOl, S102

S103, S104, S109

S105

S106

S107

S108

VR 101

*See disclaimer on p. vii.

Table 1. (Continued)

Description (Commercial description,*

if appropriate, shown in parentheses)

10 k^, 1/2 W

9.1 k^, 1/2 W

Optional. Can be used to calibrate initial

offset dial, if desired.

90.9 k^

1 kn, 1/4 W, trim-pot.

10 kfi, 1/4 W, trim-pot.

200 1/4 W, trim-pot.

20 kfi, 1/4 W, trim-pot.

10 k^2, 2 W, 15-turn, potentiometer

1 kfl, 2 W, 10-turn, potentiometer

5 kfl, 2 W, 10-turn, potentiometer

2 kfi, 2 W, 10-turn, potentiometer

22 m, 1/4 W, 5%

Dual-in-line reed relay, contact rating

10 VA (MRRIAD 12 VDC Struthers-Dunn , Inc.)

Double-pole, double- throw, 3-A @ 125 VAC

toggle switch

4 P 3-pos. toggle switch (Alco MTA406A)

[S104 wired to form 2-pole, 3-pos. switch],

6-section, reciprocal release, pushbutton

switch. (LEDEX Series 1400 pushbutton

switch) [The contacts operate when the

pushbutton is depressed, contacts remaining

operated and the button depressed until

any other button is pressed, which causes

release. The first button resets before

the second button has been pressed far

enough to operate its own contacts.]

1-pole, 12-pos. shorting type rotary switch

5-section pushbutton switch. (LEDEX Series

1400 pushbutton switch.) [4-sections:

momentary interlock, normal pushbutton

action. Contacts operate only for the time

the pushbutton is depressed.

Interlock is incorporated so that only one pushbutton can be depressed at a time.

1-section: push-push. Two-step action.

When this button is pressed once, the contacts operate and the button remains in.

When the button is pressed a second time,

the contacts and the button reset. No interlock. ] SPOT toggle switch

Constant voltage source (Analog Devices,

Type AD580).

17
Table 1. (Continued)

Schematic Reference

WlOl

W102, W103

W104

W105

YlOl

Enclosure

Digital circuit board

Description (Commercial description,*

if appropriate, shown in parentheses )

2 ft. long, 8-conductor, shielded cable.

(Shield is used as one of the conductors.)

RG58 coax cable, 2 ft. long, male BNC con- nector on both ends.

16-pin, ribbon cable, male plugs on both end

Adapter cable for use with DVM (MLOl) as a calibration instrument. This cable can also be used to check the DVM for accuracy.

Cable is RG174 coax, 3 ft. long.

Crystal, specifications: AT cut, 32 pf load

capacity, parallel resonant, 512.000 kHz.

(Optima Type K051716R, beige w/bronze trim.

Scientific Atlanta, Inc.)

(Cambion Type 715-1115-01, Cambridge

Thermionic Corporation)

with time. A digital-to-analog (D/A) converter uses this number to

produce a ramp voltage which varies linearly with time. The details

of these circuits, the digital control circuits and the analog circuits necessary to produce the desired output levels are described in

the remainder of this section.

3,1 Sweep Time Selection

The initial-to-peak sweep time, T, is the time necessary for a CLOCK

output of the SWEEP TIME SELECTION circuit (see fig. 7) to accumulate

2048^J counts on the UP/DOWN COUNTER to be described in section 3.2.

The functions of the SWEEP TIME SELECTION circuit are to produce a stable high-frequency clock signal and to modify it using "divide by n"

circuits to produce the appropriate CLOCK output.

The heart of the circuit is a crystal-controlled oscillator which can

be seen as gatet B3 in figure 7. The output is buffered by an inverter (H15) which. In turn, feeds a "divide-by-125" circuit through a NAND gate (B4). The "divide-by-125" circuit employs a 7-stage binary

counter (K) and two NAND gates (C13 and BIO). Gate C13 detects the

count of 125 (all inputs "high"tt) and resets the counter through inverter BIO. The 4.096-kHz clock signal is obtained from pin K3 because

the signal there (MSB output) is most nearly symmetrical. Note that

*See disclaimer on p. vii.

tGates and inverters will be designated by their output terminals.

ttPositive logic is assumed.

18
the gate B4 will pass the oscillator output signal only when the level

at pin B6 (marked ENABLE) is "high"; a "low" ENABLE level will terminate the sweep.

The 4.096-kHz clock signal is further modified by four programmable

stages of frequency division (E, F, G, and N) and a "divide by 2"

flip-flop (EE) to produce the desired CLOCK output at pin EE2 . Switch

S106 is used to program E, F, G, and N; i.e., to select the frequency

division factor necessary to produce the desired value of T.

3.2 Up/Down Counter and Comparator

In this circuit an up/down counter is used to convert the CLOCK output

to a binary number which will be the input for the D/A converter to be

described in section 3.5. A binary number comparator is used to determine the points at which the counter reaches "critical numbers," i.e.,

numbers corresponding to sweep maxima, sweep minima, or end of sweep.

The UP/DOWN COUNTER AND COMPARATOR circuit is shown in figure 8. Three

stages of presettable 4-bit up/down counters (S, T, and U) are used to

generate a 12-bit binary number. The starting point for all sweeps is

the number 2047^0)* This is illustrated in figure 12 which shows

the counter number sequences for the six sweep functions in the single

sweep mode. In the continuous mode of operation, the selected sweep

function is automatically and continuously repeated.

Three 4-bit binary comparators (Z, AA, and BB) are cascaded to form a 12-bit comparator which monitors the magnitude of the counter output

(A inputs) relative to a reference number (B inputs) . The truth table

for the comparator is shown in table 2.

Table 2. Truth Table for UP/DOWN Comparator.

^"\.^OUTPUT LINE AND "A>B" "A=B" "A<B" ^^^^^ LOCATION

pin 5 pin 6 pin 7 CONDITION of BB of BB of BB

A>B 1 0 0

A=B 0 1 0

A<B 0 0 1

During sweep operation, Q13 (A=B input to comparator Z) is "high." At

all other times it is "low." This inhibits an A=B output that might

otherwise occur during the switching associated with selection of the

sweep function. Under certain switching conditions, if there were an

19
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20
A=B output, the end of sweep light would go on, signaling that the

sweep had ended before it had begun.

Two additional gates are used to monitor the state of the 12-bit output. NOR gate Yll detects a minimum count of zero (all 12 outputs

"low") in the following manner. The carry-out signal at pin 7 of

counter U is normally "high" and goes "low" only when the counter

reaches its maximum count in the up mode, or its minimum count in the

down mode. Since a low at the carry-out terminal indicates eithev a minimum or a maximum count, additional information is required to resolve the ambiguity. A "low" at the A>B output indicates that the

counter is below the starting count of 2047 (iq) • ^ "high" output at

gate Yll (labeled MIN) indicates that both of its inputs are "low" and

that the counter output is at a minimum. A maximum count of 4095 (10)

(all twelve outputs "high") is detected in a similar manner by gate

YIO. A "low" at the A<B output indicates that the counter is above

the starting count of 2047 (io)« ^ "high" output at gate YIO (labeled

MAX) indicates that both of its inputs are low and that the counter is

at a maximum.

3.3 Sweep Function Selection

The selection of the SWEEP FUNCTION is made by depressing one of the

pushbuttons of S105 as indicated in figure 9. A mechanical interlock

prevents the depression of more than one pushbutton at a time. Figure 9 also contains the logic circuitry that determines when a single

sweep is terminated (assuming that it is not terminated by pressing

the RESET button). The termination of a single sweep will occur when

any of the 8 inputs to NAND gate J13 becomes "low." The required con- ditions for this to occur for each of the sweep functions is shown in

table 3. They may be checked by referring to figure 9. The first six

entries in the table are termination conditions for single sweeps

during which neither the RETUEN nor RESET buttons have been depressed.

The 7th entry describes the termination conditions after the RETURN

button has been pushed.

3.4 Sweep Command Circuit

The SWEEP COMMAND CIRCUIT in figure 10 comprises five subcircuits which

can be considered according to the purpose served by each: (a) COMMAND

pushbutton switches and associated circuitry, (b) DIRECTION circuit

(c) SWEEP STATUS indicators, (d) AUTO PEN control circuit, and (e) CONTINUOUS restart circuit.

(a) Command Pushbutton Switches and Associated Circuitry

To initiate a sweep, all inputs to gate P6 must be "low"; this will

produce a "high" on the ENABLE line. A "low" at input pin 3 of gate

P6 indicates that one of the SWEEP FUNCTION pushbuttons is depressed.

When the RESET button is depressed, the flip-flop Ql is reset producing

a "low" at input pin 4 and a "high" at input pin 5 of gate P6. This

"high" at input pin 5 is changed to a "low" by depressing the GO pushbutton. 21
1 Table 3. Conditions Required for the Termlnatlon of a Slngle Sweep

Sweep Function Required Conditions

1 (a) S105-1 depressed

(b) MAX level "high"

2 (a) S105-2 depressed

(b) MIN level "high"

(a) S105-3 depressed

(b) NORMAL DIRECTION level "high"

(c) A=B level "high"

4 (a) S105-4 depressed

(b) ^JORMAL DIRECTION level "high"

(c) A=B level "high"

5

(a) S105-5 depressed

(b) MIN level "high"

(c) A=B level "high"

6 (a) S105-6 depressed

(b) MAX level "high"

(c) A=B level "hieh"

Any (a) RETURN button previously

depressed

(b) A=B level "high'

The HOLD pushbutton stops the sweep by resetting Q13, thereby changing

the previous "low" at input pin 5 of P6 to a "high."

The RETURN pushbutton unconditionally returns the sweep to its starting

point at its previous rate. Here, flip-flop Ql is "clocked" to its

reset state and flip-flop Q13 is set through gates PIG and X4.

22
The RESET command may be generated in three ways:

(1) When the LOGIC POWER switch is initially turned on, the

charging time constant of (R103) x (C104) produces a low at input pin 13 of gate RIO for a time sufficient to

insure reset.

(2) From the continuous restart circuit gate V12.

(3) From the RESET pushbutton switch.

(b) Direction Circuit

The direction of the UP/DOWN COUNTER is determined by the level of the

RUNNING DIRECTION line; a "high" corresponds to UP, a "low" correspond

to DOWN. When the RESET pushbutton is depressed, RUNNING DIRECTION

control is transferred to gate X3 by flip-flop Wl. At this time the

output Wl is "high" and the output X3 is gated to the RUNNING DIRECTION line through AND/OR-select gate Lll. The RUNNING DIRECTION at

the start of a sweep is controlled by the gate P9; for SWEEP FUNCTIONS

1, 3, and 5 it is UP; for 2, 4, and 6 it is DOWN. When the maximum

or minimum count is reached, the RUNNING DIRECTION is reversed by flip

flop EE13 and exclusive-OR gate X3. Pin 2 of gate X3 determines

whether the level at pin 1 becomes inverted at the output or not; i.e. a "high" level at pin 2 causes inversion, a "low" level does not.

During a sweep in which the RETURN pushbutton is not depressed, the

NORMAL DIRECTION and RUNNING DIRECTION are the same.

If the RETURN pushbutton is depressed, the NORMAL DIRECTION level is

not altered, but the RUNNING DIRECTION level may be altered through

flip-flop W13, depending upon the levels of the A>B and NORMAL DIRECTION lines. If the levels of A>B and NORMAL DIRECTION are both "high"

or both "low," the RUNNING DIRECTION level will be changed; if the

A>B level is "high" and the NORMAL DIRECTION level is "low" (or vice

versa), the RUNNING DIRECTION will not be changed.

It should be noted that although pressing the RESET pushbutton sets

the COMPARATOR reference number to 2047 (lO) > pressing the RETURN

pushbutton changes the COMPARATOR reference number to 2048 by setting

flip-flop Wl, which, in turn, changes the output levels of the AND-OR

eates L12 and L13. This is done for the following reason. In the

RESET condition, A=B and the A>B level is "low." This would cause the

COUNTER to immediately start to count up if the RETURN pushbutton were

pressed after RESET. In this case, the SWEEP is forced to end after

one count by the change of reference number just described. This results in an offset of the output voltage at any END of SWEEP caused

by pressing the RETURN pushbutton. The amount of this offset (1 part

in 2047) is undetectable in normal use.

(c) Sweep Status Indicators

Four LEDs (light-emitting diodes) are used to indicate the operating

state of the SWEEP. Only one LED (at most) can be on at a given time

during a normal sequence of COMMAm)s. When the ENABLE level from

23
gate P6 is "high," either the UP or DOWN LED will be on, depending

upon whether the RUNNING DIRECTION level is "high" or "low." Depressing the HOLD pushbutton sets flip-flop DD13, which turns on the HOLD

LED through inverter HID. If the sweep is resumed by pressing the

GO pushbutton, flip-flop DD13 is clocked to its "reset" state. The

END LED turns on at termination of the SWEEP when flip-flop Ql is set

by a "high" level at J13. When the RESET pushbutton is depressed,

any previously turned-on LED is turned off. Thus, if all LEDs are off

it signifies that RESET has taken place.

(d) Pen Control Circuit

Both inputs to NAND gate Bll must be "high" to energize the PEN relay

RLlOl. Thus, the PEN control circuit will be closed only when the

AUTO PEN switch is in the ENABLE position and the ENABLE level is

"high."

(e) Continuous Restart Circuit

A decade counter, FF, is used to generate (1) a RESET pulse via inverter V12 and NAND gate RIO; (2) a "start" pulse via NOR gate PIG and

exclusive-OR gate X4 ; and (3) a "self-turnof f pulse: via NAND gate Oil

and NOR gate Y4 in the following manner. A "high" from NAND gate J13

signifies the end of a sweep and sets flip-flop Ql. A "high" from pin

Ql clocks flip-flop DDI to its "set" state when the SINGLE-CONTINUOUS

switch is in the CONTINUOUS position. This causes a "low" level at

the clock enable line FF13 of the counter* FF, allowing it to start

counting 512 kHz pulses from the oscillator buffer-inverter H15.

First, the RESET pulse is generated from gate V12; next, the "start"

pulse from X4 sets Q13 (this is equivalent to a GO command), and

finally, the counter is "disabled" by the "self-tumoff pulse" from Y4

which resets flip-flop DDI, bringing the clock enable line of the

counter "high" preventing further counts. This sequence is repeated

continuously if the SINGLE-CONTINUOUS switch remains in the CONTINUOUS

position.

If, at the end of the sweep, this switch is in the SINGLE position,

flip-flop DDI is clocked to its "reset" state, in which case, the

counter-clock enable level is "high," and counting is inhibited.

3.5 Analog Circuit

The digital circuit produces a 12-bit binary number which varies

linearly with time. The heart of the analog circuit is a digital to

analog (D/A) converter which uses this time-varying binary number to

produce a voltage which varies linearly with time. A series of dc

amplifiers is used to make this voltage bipolar and to obtain the desired amplitude and offset levels.

*For this counter, the "clock enable level" must be "low" to enable

counting; a "high" level disables or inhibits counting.

24
Current from the D/A converter AR C (fig. 11) develops a voltage across

an internal load resistor. This voltage is passed through amplifier

AR B to provide a basic single-ended sweep signal. A portion of this

is selected by adjusting the SWEEP AMPLITUDE and TRIM potentiometers

and then summed with an INITIAL OFFSET voltage through amplifier AR D

to produce the -10 V output. This output is inverted by amplifier AR F

to produce the +10 V output. Amplifiers AR G and AR H are used to

raise these levels to provide the +100 V and -100 V outputs, respectively.

The voltage regulator VRlOl provides a stable 2.5-V (nominal) level which

is used as a reference for the D/A converter and a source of INITIAL

OFFSET voltage. An INITIAL OFFSET voltage of opposite polarity is

obtained by using an inverter, AR A. The instrumentation amplifier

AR E is used to provide a single-ended output labeled ANALOG OUTPUT

which is equal to one-half the difference between that at the +10 V

and -10 V output terminals. It is intended for monitoring the sweep

generator output with an instrument having one input terminal grounded.

3.6 Power Supplies and Metering

The schematic circuit diagram of the POWER SUPPLIES AND METERING for

the control module is shown in figure 13,

4. CIRCUIT DETAILS OF HIGH-VOLTAGE AMPLIFIER MODULE

A schematic diagram of the power supplies and switching for the HVAM

is shown in figure 14. The high-voltage amplifier consists of two substantially identical amplifiers, one of which is driven in the positive

direction while the other is driven in the negative direction, and vice

versa. The two amplifiers are represented schematically in the right

and left halves of figure 15. The electrical components shown in

figures 14 and 15 are described in table 4. The circuit description

which follows refers only to the right side of figure 15, the amplifier which produces the "+" output. Overall feedback from the output

to the input of the driver section linearizes the transfer function

and "regulates out" power supply variations.

4,1 General Specifications

Each amplifier, when driven by a signal in the range -10 to +10 V,

produces a signal proportional to the negative of the input signal.

The proportionality constant (gain) is selectable such that -10 V input will produce outputs of 0.5, 1.25, 2.5, 5.0, and 12.5 kV. The circuit is such that +10 V input produces the negatives of the voltages

indicated above. The amplifiers can drive a 50-M^^2 external load.

The anticipated voltage sweep rates are low so that capacitive loading

of the output is not a problem.

4.2 Output Stage

The output stage is the most challenging design, having to be constructed within the capabilities of available tubes, and controls what

25
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27
28
Table 4. Electrical Parts List for HV Amplifier Module

Schematic Reference

A201, A202, A203, A204

AR201, AR202, AR203, AR204

C201, C202

C203, C204, C205, C206 ) C207, C208, C209, C210 /

C211, C212

C213, C214 (Gimmick capacitor)

D201, D202, D203, D204

D206, D207, D208, D209

D205

DS201, DS202, DS203

E201, E202

J201, J202, J204

J203

J205, J206

J207, J208

J209, J210, J211, J212

J213, J214, J215, J216

P201

PS201, PS202

PS203

Q201, Q202, Q203, Q204

R201, R202

R203, R204, R205, R206

R209, R210

*See disclaimer on p. vii.

Description (Commercial description,*

if appropriate, shown in parentheses)

50 kV optical coupler (Optron, Type

OPI-150)

General purpose FET operational amplifier

(Teledyne Philbrick, type 1421).

500 yF, 50 VDC, electrolytic capacitor

50 yF, 50 VDC electrolytic capacitor

0.01 pF, 50 V, ceramic capacitor

3/4" length of copper braid around output

cable covered with shrinkable tubing.

IN4005 diode

IN4005 diode

18DB6A bridge rectifer

24 V indicator lights

Corona ring, high-voltage terminal

Insulated BNC coaxial chassis connector

(Amphenol type 31-010)

8-pin cable female connector, "Jones"

type (Cinch type S-308-CCT)

High-voltage coaxial chassis connector

(Amphenol type 97-3102A-18-420S)

HV connector assembly

Sub-minax coax cable connector

(Amphenol type 27-7)

Sub-minax receptacle (Amphenol type 27-9).

8-pln chassis male connector, "Jones" type

(Cinch type P-308-AB)

Power supply, 20 kV, dc, (? 1 mA (Del,

type 20-1-4)

Power supply, regulated with +15 V and -15

outputs (3 100 mA (Acopian type D15-10A)

.

2N4036 transistor.

50 m, 5 W, 5%. (IRC Type MVP)

100 m, 15 W, 1%. (Caddock Type MG815)

1.2 m, 1/4 W, 1%. (Caddock Type MG650)

29
Table 4. (Continued)

Schematic Reference

R211, R212

R213, R214

R215, R216

R217, R218

R219, R220

R223, R224

R22 7, R228

R231, R232

R235, R236

R239, R241

R240, R242

R243, R244

R245, R246

R249, R250

R254

RL201, RL202, RL203, RL204

RL205

S201

T201, T202

T203

, R221, R222

, R225, R226

, R229, R230

, R233, R234

, R237, R238

, R247, R248

, R251, R252, R253,

(Caddock Type MG650)

U201

V201, V202, V203, V204

Description (CoTnmerclal description,*

If appropriate, shown In parentheses)

400 kfi, 1/4 W, 1%/

200 kn, 1/4 W, 1%.

120 kfi, 1/4 W, 1%.

80 kf2, 1/4 W, 1%.

1 MQ, 1/2 W, 5%.

4.3 kf2, 1/2 W, 5%.

10 kfi, 1/2 W, 5%.

10 kfl, 1/2 W, 5%.

10 kQ, 1/2 W, 5%.

7.5 kfi, 1/2 W, 5%.

47 kfi, 1/2 W, 5%.

20 kfi, 1/2 W, 5%.

1 kfi, 1/2 W, 5%.

10 k^, 1/4 W, 15-tum trim-pot

High-voltage relay (ITT Jennings,

Type RE6B-26-N300)

.

Time-delay relay (Guardian TD062C30-115A)

.

2-pole, 5-posltlon, shorting type rotary swlt

Transformer (Stancor, Type P6377).

High-voltage isolation transformer.

(NWL Model 24543).

24 V dc regulator.

Vacuum tube 6BK4C/6EL4A.

Miscellaneous

4 - Tube sockets (Amphenol, Type 78S8-1M-0125)

4 - Cap and lead assembly for V101-V104 (RCA 114048)

*See disclaimer on p. vii.

30
the drivers must do. Therefore, the output stage is the starting point

of the description. The 6BK4C tube is rated to withstand 27 kV plate

to cathode and has maximum power and current ratings of 40 W and

L.6 mA, respectively. With the effective load resistance of 25 MJi external load in parallel with internal load) the current

limitation is more restrictive than the power limit. The 6BK4C is intended as a shunt regulator tube so it is not designed to have a low

voltage drop at zero grid bias. With a 20-kV power supply and 25-M^^

load the zero-bias plate voltage is about 5 kV. With a +20 kV power

supply, the swing is thus limited to +15 kV. With the usual 20%

tolerance on tube specifications the actual limits may be as low as

fl3 kV. When one tube is zero-biased, the other one is cut off and has

approximately 35 kV across it. The rated voltage is then exceeded substantially at the limits of the swing. This undesirable condition is

accepted because no higher-rated tube is available; there is no other

choice. However, the rating is based on leakage developing due to

glass electrolysis when the voltage is maintained constant as it is in

shunt regulator service. In the present service, the time the tube

spends under maximum voltage stress is much less than 100% of the

operating time, so electrolysis will proceed more slowly. Also, the

temperature of the bulb is low since the dissipation is much less

than the allowed 40 W. Electrolysis rate increases as an exponential

of the absolute temperature. Life of the 6BK4C's is expected to be

reasonable, and the chance of having to replace tubes was taken as a calculated risk. Although our use experience is limited (several

hundred hours over a period of approximately one year), no failures

tiave occurred thus far.

Each tube has a floating 28-V negative-bias supply which is derived

from a 20-V winding of T203 . The 6.3-V tap on the same winding provides heater current. V204 and V202 (of the other amplifier) share the

winding which is connected to the -20 kV power supply. The 10-kfJ

grid resistors (R229 for V203, and R230 for V204) bias the grids to

0 V when the transistors of the optical couplers, A203 and A204, are

cut off. The high-voltage power supplies should not be turned on with

the driver circuits disconnected since approximately 3 mA per tube

would flow, exceeding both the current and power ratings of the tubes.

With properly adjusted drivers connected, tubes are not both biased

n simultaneously. When the light-emitting diode of A203 is turned on,

the transistor of A203 conducts, biasing V203 toward cutoff. When A203

is driven on, A204 is driven off so that V203 is turned off as V204 is

turned on, and the output voltage swings in a negative direction. The

maximum negative bias for the tubes is about 20 V when the optical

coupler transistors are full on. R225 and R229 form a voltage divider

with a ratio of approximately 0.7. Thus, 20 V should be enough to cut

the tubes off at 35-kV plate voltage based on an extrapolation of published curves. Tubes at the limit of the allowable +20% tolerances

might not cut off. In our experience, however, none of the ten tubes

tried failed to operate as desired.

The optical couplers, A203 and A204, have a transfer ratio of about

0.7. About 2 mA must flow to bias the tube off, which means about 3 mA

in the LED.

31
The bias supplies are typical half-v/ave RC-filtered power supplies and

are unregulated. Bias variations are taken out by the overall feedback,

4.3 Driver Circuit

The dividing line between the output circuit and the driver circuit

bisects the optical couplers and the feedback resistors. All parts of

the driver circuits are within +15 V of ground.

Transistors Q203 and Q204 drive the LED's of the optical couplers.

The LED currents are limited by series resistors R247 and R248 to less

than 30 mA. R233 and R234 limit the base currents of Q203 and Q204

to conservative values; these values allov7 adequate drive and also

avoid loading the outputs of AR203 and AR204,

AR204 is operated as a unity-gain inverter to provide the inverted

drive for V203. Additional current is injected into the node at pin 2 to provide a dc offset in the output. This offset is used to establish the quiescent current in the output tubes at 0 V output. See

Section 5,2 for a discussion of hov/ the quiescent point is established.

AR203 is operated locally open-loop at dc to provide a high gain near

the overall amplifier summing point. The local feedback provided by

R240, R241 and C212 produces a high-frequency roll-off to stabilize

the overall feedback amplifier. The overall feedback summing point is

at the + input of AR203, which is the - input if the whole amplifier

is considered as a unit. Diodes D212 and D213 protect this input

from the inevitable surges which occur in high-voltage equipment, R206

and C214 in parallel provide the overall feedback path and establish

main frequency roll-off of the whole amplifier. C214 is about 2,5 cm

of braid around the output cable which produces a capacitance of about

2 pF,

The overall gain is established by choosing the input resistor with

S201B (a make-before-break selector switch). The input resistance is

varied from 80 k^^ to 2 MQ,

5. CALIBRATION AND ADJUSTMENTS

5.1 Bias Supply Control Module

a. Digital Circuit

No adjustments are necessary or possible.

b. Analog Circuit

Either the digital voltmeter (DVM) in the control module or a separate

DVM may be used for calibration and adjustment of the ANALOG CIRCUIT.

If the internal DVM is to be used, it will be necessary to install an

32
adaptor cable (W105) to receptacle J103 at the rear of the control

module; the leads will be connected to the DVM when the METER RANGE

switch is in the HV position. The internal DVM should be checked for

accuracy before proceeding with the ANALOG CIRCUIT calibration.

(1) Initial Offset Calibration

(i) Remove VRlOl from its socket and connect a short jumper

wire between the output and ground terminals on the

socket. This will provide 0.00 V input to AR A.

(ii) Measure the output of AR A with a DVM and adjust trimpot A-ZERO for 0.00 V output,

(iii) Remove the jumper wire and reinstall VRIOI.

(iv) Measure the output from VRlOl and record the value,

(v) Reverse the meter leads''^ measure the output of AR A,

and adjust trim-pot A-TRIM to obtain the same reading

as that previously obtained from the output of VRlOl.

(2) Zero adjustment of AR B

(i) Connect the DVM to the output of AR B (pin 6).

(ii) Momentarily depress the RESET button; then adjust

B-ZERO for 0.00 V output.

(3) Zero adjustments of AR D, AR E, AR F , AR G, and AR H

(i) Set SWEEP AMPLITUDE and associated TRIM completely

counterclockwise (CCW) . Set INITIAL OFFSET and

associated TRIM completely CCW; set INITIAL OFFSET

switch to ZERO. Carry out following steps in

sequence

.

(ii) Connect DVM to AR D output at -10 V BNC connector

(J108) or pin 6 of AR D and adjust D-ZERO for 0.00 V

meter reading.

(iii) Connect DVM to AR F output at +10 V BNC connector

(J107) or pin 6 of AR F and adjust F-ZERO for 0.00 V

meter reading.

(iv) Connect DVM to AR E output at ANALOG OUTPUT connector

(J109) or pin 7 of AR E and adjust E-ZERO for 0.00 V

meter reading,

(v) Connect DVM to AR G output at +100 V UHF connector

(JllO) and adjust G-ZERO for 0.00 V meter reading,

(vi) Connect DVM to AR H output at -100 V UHF connector

(Jill) and adjust H-ZERO for 0.00 V meter reading.

''For best results (greatest accuracy) the polarity of the DVM should

be the same for all measurements.

33
(4) Amplifier tracking (gain) adjustments

(1) Adjust D-TRIM to approximate center of rotational range.

(11) Select SWEEP FUNCTION 1 (Ascending single ramp) and

a low INITIAL TO PEAK SWEEP TIME. Momentarily depress

the RESET pushbutton and then the GO pushbutton. After

the END of SWEEP light comes on, adjust the SWEEP

AMPLITUDE CONTROL for exactly -5.00 V at the -10 V

output connector. Carry out the following steps in

sequence.

(Ill) Connect DVM to AR F output and adjust F-TRIM for a +5.00 meter reading.

(Iv) Connect DVM to AR G output and adjust G-TRIM for a +50.00 meter reading,

(v) Connect DVM to AR H output and adjust H-TRIM for a -50.00 V meter reading,

(vl) Connect DVM to ANALOG OUTPUT and adjust E-TRIM for a +5.00 V meter reading.

This completes the ANALOG CIRCUIT calibration.

5.2 High-Voltage Amplifier Module

Only 3 adjustments are provided. The zero-offset adjustments provided

on AR203 and AR204 by R252 and R253 respectively are noncrltlcal and

need adjustment only If the associated amplifier Is replaced. The

quiescent point adjustment may be needed If the replacement of one or more tubes Is required. The overall feedback maintains the amplifier

performance quite well even If these adjustments are not optimized.

Remove time-delay relay from Its socket. This will prevent accidental

high-voltage turn-on.

a. Zero-Offset Adjustment

1. Remove both operational amplifiers from high-voltage driver

board

.

2. Measure the slider voltage of R254 (It can be accessed at

the end of R244 that Is nearer the center of R254) with an

external DVM and adjust the center trim-pot, R254, for

0.00 V.

3. Temporarily connect a 10-MQ resistor between pin 2 and 6

of operational amplifier AR203. Switch high-voltage range

switch to 25 kV and Install both operational amplifiers.

4. Short the -10 V driver connector, J201. Turn power switch

to standby and adjust zero-offset trim-pot, R252, near operational amplifier AR203 for 0.00 V reading on operational amplifier output pin 6.

5. Measure the output of operational amplifier AR204 pin 6

and adjust the trim-pot nearest AR204 for 0.00 V. Remove

short across -10 V drive and 10-Mf2 resistor. Reinsert the

time delay relay.

34
As mentioned in section 4.3, the balance potentiometer R254 is used to

establish the quiescent operating current in V203 and V204. With zero volts input the overall feedback will cause the intermediate signal

voltages in the amplifier to assume values which will bring the output

voltage to zero. When the output voltage is zero equal currents flow

in V203 and V204. Producing an offset voltage in that povtion of the

eirowLt which drives V20S but does not affect the drive to V204 will

change the quiescent current. The adjustments described above reduced this offset to zero.

b. Quiescent Point Adjustment

While the voltages and currents in the high-voltage amplifier may not

be lethal, contact with them would certainly be unpleasant. Before

starting the following procedure, power must be off and grounds con- nected to the output and both power supply corona caps. Remove the

connector from the plate V204 and connect a 200- yA meter from the

connector to the cap. The + of the meter goes to the connector. The

meter must be insulated so there is at least 2 or 3 cm between it and

the nearest conductors. The measurement will be made with the meter

near ground but transients may occur during turn-on. With the meter

securely in place where it can be read easily, remove the grounds and

go through normal turn-on procedure. With the input at 0.00 V, check

that the output is also 0.00 V. Then, adjust R254 for a quiescent

current between 5 and 50 uA. The output should still be 0.00 V. Shut

off the power, ground the output and power supplies, remove the meter,

and replace the plate cap.

The procedure for adjusting the amplifier on the left side of figure 15

is exactly the same except, of course, that the component designation

numbers are different.

ACKNOWLEDGMENT

The authors acknowledge with gratitude many helpful suggestions contributed by Jeremiah Avins during the development of the equipment described in this report.

35
il
APPENDIX A

This appendix contains information which is intended for use by anyone

who wants to duplicate the Bias Supply Control Module described in

the body of the report. It consists of:

(i) A list of the mechanical parts which are not commercially

available, (table 5)

(ii) detailed drawings of those parts, and

(iii) Drawings and photographs showing the placement of the

mechanical parts and electrical components identified

in tables 1 and 5.

Table 5. List of Mechanical Parts in Bias Supply Control

Module (not commercially available)

Part No. Part Description Drawing No.

1 Front panel MAI

2 Rear panel MA2

3 Base panel MA3

4 Clamp for power supply PS102 MA3

5 Clamp for power supply PS103 MA3

6 Analog printed-circuit board MA7

37
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16-PIN DUAL IN-LINE

PLUG TOP VIEW

Figure MA6. Cables WlOl, W105, and crystal circuit

subassembly, bias supply control module.

43

ANALOG DIGITAL

Figure Al. Top view of bias supply control module

with top cover removed.

45
Figure A2 . Top view of analog circuit board, bias

supply control module.

46
APPENDIX B

This appendix contains information which is intended for use by anyone

who wants to duplicate the High Voltage Amplifier Module described

in the body of the report. It consists of:

(i) A list of the mechanical parts which are not commercially

available, (table 6)

(ii) detailed drawings of those parts, and

(iii) a drawing and photographs showing the placement of

the mechanical parts and electrical components identified

in tables 4 and 6.

Table 6. List of Mechanical Parts in High-Voltage Amplifier

Module (not commercially available)

Part No. Part Description Drawing No.

1 Front Panel MBl

2 Rear Panel MB2

3 Base Panel MB3

4 Left Side Panel MB 4

5 Right Side Panel MB4

6 Chassis Top Cover MB5

7 Chassis Bottom Cover MB5

8 HV Connector Assembly MB6

9 Driver Printed -Circuit Board mi

10 HV Amplifier Printed-Circuit Board MBS

11 Clamp For Power Supply PS203 MBll

47
5

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53

55
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56
57
Figure Bl. Top view of HV amplifier module with top cover removed.

58
Figure B2. Top view of HV amplifier board.

59
60
REFERENCES

1. Goodman, A. M. , A Useful Modification of the Technique for Measuring

Capacitance as a Function of Voltage, IEEE Trans. Electron Devices

ED-21 , 153-151 (1974).

2. Goodman, A. M. , An Investigation of the Silicon-Sapphire Interface

Using the MIS Capacitance Method, IEEE Trans. Electron Devices

ED-22 , 63-65 (1975).

3. Goodman, A. M. , Semiconductor Measurement Technology: Safe Operation

of Capacitance Meters Using High Applied-Bias Voltage, NBS Special

Publication 400-34 (December 1976).

4. Goodman, A. M. , Semiconductor Measurement Technology. Suppression

of Premature Dielectric Breakdown for High-Voltage Capacitance

Measurements, NBS Special Publication 400-37 (July 1977).

5. Goodman, A. M. , Semiconductor Measurement Technology: A 25-kV

Bias-Isolation Unit for 1-MHz Capacitance and Conductance Measurements, NBS Special Publication 400-40 (September 1977).

61
NBS414A (REV, 7-73)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUl^LICATION OR REPORT NO. NBS SP 400-41

2. Gov't Accession

No.

3, Recipient's Acces.sion No.

4. tiTLE AND SUBTITLE

Semioonduotov Measupement Technology:

A Versatile High-Voltage Bias Supply for Extended

Range MIS C(V) and G(V) Measurements

5. Publication Date December 1977

6. Performing Organization Code

7. AUTHOR(S)

Paul Kuczer, Harvey 0. Hook, and Alvin M. Goodman

8. Performing Organ. Report No.

9. PEl^FORMING ORGANIZATION NAME AND ADDRESS

RCA Laboratories

Princeton, New Jersey 08540

10. Proieet/Task/Work Unit No.

11. Contract/Grant No. 5-35912

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

NBS - Washington, D.C. 20234

ARPA - Arlington, Virginia 22209

13. Type of Report & Period Covered Special Report

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

This work was funded by the Defense Advanced Research Projects Agency under ARPA

Order 2397, Program Code 6D10.

16. ABSTRAC^T (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.)

Recently developed technology has enabled the measurement of MIS C(V) and

G(V) at bias-voltage magnitudes as large as 25 kV. This report describes a versatile high-voltage power supply intended for use as a bias source in carrying out such measurements.

The design allows the user a wide variety of options in the selection of

the sweep function (waveform), sweep time, initial bias voltage, and the amplitude of the bias sweep. There are six possible sweep functions: (i) increasing

ramp, (ii) decreasing ramp, (iii) positive polarity half-wave sawtooth /( increasing

/ramp followed by decreasing ramp), (iv) negative polarity half-wave sawtooth (decreasing ramp followed by increasing ramp) , (v) full-wave sawtooth starting with

increasing ramp, and (vi) full-wave sawtooth starting with decreasing ramp.

Either single or repetitive sweeps may be selected. The sweep time from the

initial value to the end of the first ramp segment may be varied from 1 to 2000 s. Operator convenience is enhanced by certain features of the design;

among these are light-emitting diodes which |display the state of the sweep

and automatic pen control if the sweep is used with an x-y recorder.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

High-voltage bias supply; high-voltage C(V) and G(V) measurements; high-voltage

function generator; high-voltage sweep ; semiconductor devices; silicon-on-sapphire

measurements

.

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