Epson L90P - TM Two-color Thermal Line Printer Instrukcja Użytkownika Pobierz pdf (Strona 32)

Build

a Pos-Neg

Pulse Generator

INDISPENSABLE

TRIGGER

SOURCE FOR DIGITAL

CIRCUITS

BY FRANK H. TOOKER

4.7K

NEG C2

.01yF

POS

.O229F

4.7K

+9V

OUTPUT

Fig.

Simple unijunction transistor

circuit

generates positive

negative

pulses

relatively

wide

durations.

I N THE

COURSE of experimenting

with,

developing,

and

testing

computer logic

and counter

circuits, it is

useful, if not

essential,

have

available source

pulses

to supply triggers

or actuating

sig-

nals.

Such a source should

provide pulses

that are quite

narrow,

of adequate am-

plitude,

and either positive

or negative

in polarity,

selectable at

the

flick

a switch.

The

circuit shown in Fig. 1 is

satis-

factory

for

number

applications.

Output

amplitude

good,

and

the

setup

is quick

and easy to breadboard

in an

emergency. Pulse duration

wide,

how-

ever.

the circuit shown in

Fig. 2,

in-

ductor,

Li,

with a fairly high Q is

used

the

circuit of

Qi,

rather

than a

re-

sistor. Both Bi

and the

low

end

of timing

capacitor Cl are grounded.

Each time

the UJT fires,

negative

pulse and

positive pulse

are

produced

consecutive-

SOmH

1000

.0229F

1N19

POS

NEG

IN191

47K

20K

+9V

1000PF

PUT

Fig. 2. This circuit

generates

positive and

negative pulses

simultaneously

with

the

shape

of the

pulse

sharpened

the

inductor

the

base

circuit.

POPULAR ELECTRONICS

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