Datapulse 101 - Page 22

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1

A

detailed

circuit

description

is

obtained

by

substituting

the

corresponding

circuit

component

in

the

detailed

description

of

the

delay

multivibrator

circuit.

3.2.9

Gate

Emitter

Follower

In

addition

to

operating

as

a

steering

diode

for the

delay

multi-

vibrator

input,

CR51

is

used

to

inhibit

triggers

from

QB

(trigger

multi—

vibrator

pulse

shaper)

when

the

gate

waveform

at

the

base

of

Q9

is

in

its

positive

or

inhibit

condition.

This

gate

depends

on

the

fact that

the

collector

of

Q8

can

be

readily

raised

by

the

emitter

of

Q9

in

such

a

manner

as

to

back

bias

CRSI

sufficiently

to

prevent

the

passage

of

triggers

from

08-

The

resistor

divider

(R50

and

R51)

in

the

base

of

Q9

serves

to

set the

gate

waveform

level

at

the

emitter

of

Q9

to

the

dc

level

for

proper

gating

operation

of

the

delay

multivibrator.

3.2.

10

External

Trigger

Amplifier

The

external

trigger

amplifier

consists

of

transistors

Q5

and

Q6

and

the

associated

switching

circuits.

The

transistors

are

arranged

as

an

emitter

coupled

differential

amplifier

centered

about

ground.

The

dc

component

of

the input

signal

is

removed

by

coupling

capacitors

C31

and

C32

while

the

triggering

level

potentiometer,

R36,

makes

it

possible

to

re-establilh

ground

at

any

desired

point

on

the

incoming

waveform.

Either

a

noninverted

output

from 06

or

the

inverted

phase

from

05

is

applied

to

the

trigger

multivibrator

depending

on

which

collector

is

supplied

current

from

+12

volts.

This

is

controlled

by

the

two

external

trigger

positions

of

the

repetition

rate

selector

switch.

The

output

from

the

collector

being

used

is

applied

to

the

trigger

multivibrator

through

diode

CR30

or

CR31

while

+6

volts

is

applied

to

the

unused

collector

through

either

CR32

or

CR33.

For

example,

in

the

positive

external

trigger

mode,

Q6

supplies

its

output

through

CR31

and

receives

collector

current

from

+12

volts

while

Q5

is

prevented

from

contributing

to

the

output

because

CR30

is

back

biased

by

the

drop

across

CR32.

.—

_L..

L.

L. L. L.

L. L. L.

The

output

is

applied

to

the

tunnel

diode

of

the

trigger

multivibrator

which

requires

5

milliamperes

to

swing

it

from

one

state

to

the

other.

Therefore

the

input

sensitivity

is

determined

by

the

input

required

to

supply

this

5

milliamperes.

3.2.

11

Single

Cycle

Operation

The

single

pulse

pushbutton

trips

the

trigger

multivibrator

by

current

made

available

from

+12

volts

by

the single

pulse

position

of

the

repetition

rate

selector

switch.

The

trigger

amplifier

circuit

is

disabled

in this

mode

because

neither

collector

is

supplied

current

from

+12

volts.

Switch

chatter

is

decoupled

by

resistor

R34

and

capacitor

C30.

3-7

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