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42

[ ual

transistor

U5/303

is

located

in

the

feedback

path

to

reduce

the

load

effects

of

the

inverting

inputs

of

a

nplifier

U/ 5

351

and

352.

By

means

of

resistor U5/60511606

the

offset

voltage

at

the

output

of

the

voltage-

c

ment

converter

is

adjusted

to

zero

between

the

emitter

connections

of

U5/301

and

305.

[iode

U5/401

limits

the

voltage

at

the

input

SWEEP

IN

to

12 V

maximum.

F or

time-asymmetrical

operation

(duty

cycle

0.1

or

0.9)

two

different

charging

currents

are

required.

For

this,

t l

le

controi

unit

contains

another

pair

of

voltage-current

converters

(U5/353,

354,

312,

314,

316),

which

is

c >ntrolled

by

the

same

differential

voltage.

Amplifier

pair

U5/

353,

354

is

electrically

identical

to

pair

L

5/351

/

352

and

adjusted

correspondingly.

1 he resistors

on

wafer

4,

switch

U2,

which

determine

charging

time

and

frequency,

have

twice

the

value

of

the

c

mesponding

resistors

on

wafer

2,

switch

U2.

The

output

currents

±0,5.

I

obtained

are

amplified

by

10

in

two

c

ment

mirrors

U5/317-320

and

made

±5

I.

For

asymmetrical

operation

voltage-current

converters

U5/351,

352

supply

currents

±5

1/9 via

the

corresponding

c

Irrent

mirrors

.

III

this

case

resistors

U2/617

to

620

are

used

whose

values are

9/5

higher

than

those

of

the

corresponding

rl

sistors

U2/608

to

611.

3.1.3.3.

1"e

output

currents

of

the

voltage-current

converters

are

"reflected"

by

each

a

current-mirror

pair

in

ratio

1: 1

O'

10: 1

and

supplied

to

the

oscillator.

The

current

mirrors

are

mainly

made

of

a series

diode

(e.g.

U5/306)

-r

~sistor;

see

example

in

fig. 8.

11e

collector

current

liN

of

voltage-current

converter

U5/301

flows

through

the

current

mirror.

The

resulting

v'Jltage

drop

controls

a

current

back

fed

emitter-stage,

e.g.

U5/305,

which

supplies

the

output

current

IOUT.

jj

ssume

the

current-voltage

characteristics

of

e.

g.

diode

U5/306

(transistor

used

as

diode)

and

the

emitter-base

d

ode

of

the

output

transistor

(e.g.

U5/308)

are

identical

as weil as

their

relevant

resistors_

The

ratio

II

N/IOUT

tl

l

en

is

1: 1;

otherwise,

the

current

ratio

IOUT/11 N

is

inversely

proportional

to

the

resistance

ratio.

T1e

practical

differences

of

the

input

diodes

and

the

differences

in resistances are

compensated

by

potentiometer

(I

.g. fig. 8,

U5/620).

The

built-in

potentiometer

supplies

a

correcting

voltage,

causing

a

correcting

current

sl

,

perimposition.

T

le

base cu

rrents

which

interfer

at

low

values (II N

.;;;

lOmA)

are every

time

neutral

ized

by

potentiometers

L

5/628,

629,

672, 673.

3.1.3

.

3.1.

rhe

current

mirror

U5/308,

307

is

used

for

time-symmetrical

operation.

The

collector

current

of

transistor

L

5/308

operates

as

frequency-determining

charging

current

le

for

the

oscillator

from

the

positive

direction.

Z

,ner

diodes

Ul/423,

424

reduce

the

power

dissipation.

T

le

relevant

charging

current

le*

for

the

oscillator

is

supplied

by

voltage-current

converter

U5/352,

305

via

L

5/307.

T lis

current

mirror

forms

the

reference

for

current

mirror

U5/

308,

which

is

adjusted

by

symmetry

controi

U

5/310,

327,

328

to

I e = I e * (see

3.1.3.4.).

The

accuracy

of

the

current

mirror

for

I e *

determines

the

fr

~quency

accuracy

for

time-symmetrical

operation;

maximum

adjustment

is

obtained

by

means

of

U5/625

a

ld

629.

3.1.3.3

.2.

~urrent-mirror

pair

U5/319,

320

amplifies

the

input

current

10

times,

which

corresponds

to

the

ratio

of

rE

sistances

U5/660

to

675

or

U5/661

to

676.

These

current

mirrors

are

adjusted

by

potentiometers

U

5/665,

670.

The

Zener

diode

reduce

the

power

dissipation.

3.1.3.4

_

~

ymmetry

controi

U5/31

O

adjusts

the

charging

current

automatically

to

I e *

for

time-symmetrical

operation.

T le

symmetry

controi

is

driven

by

the

voltage

applied

between

zero

potential

and

the

smallest

potential

to

ei

rth

of

the

oscillator

capacitor,

whose

galvanic

zero

is

disconnected

by

switch

Ul/VI

for

symmetrical

o

leration.

The

controi

loop

keeps

this

potential

difference

at

a

constant

value

near

zero.

T lis

means

that

I e

and

I e * are equal.

3.1.3

.5. T le single-shot logic

contains

a flip-flop

(U5/325

and

326)

.

T le

latter

can

be

set

to

OFF

or

START

by

means

of

switch

SINGLE

SHOT

MODE; it

can

be

set

by

input

sljnal

eONTROL

INPUT

(at

the

rear)

and

reset

by

the

square-wave

signal

from

the

oscillator

.

'1\

hen

switch

SINGLE

SHOT

MODE

is

set

to

SET

PHASE,

the

static

blockade

at

point

U5/7

is

cancelled,

so

H

at

the

flip-flop

is

reset

by

the

first positive-going

square-wave

at

point

U5/e

and

U5

/

321-322.

I r

the

oscillator

u R

is

kept

to

-5

V (see

3.1.2

.

8.)

via

point

U5/X,

the

potential

of

wh

ich

jumps

from

O

to

-5

V

w len

switching-over

.

The

potentials

at

points

U5/6

and

4

jump

simultaneously

from

negative va lues

to

-5

V

ar

d

+5

V respectively.

The

start

potential

of

the

triangular

voltage

is

adjustable

within

this

voltage range

by

m

,ans

of

potentiometer

SET

PHASE.

....

-

-

-

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