Boss Audio Systems BV8.5GA User Manual download pdf (Page 88)

developing

fixed

-level

square -wave

output signal with

a peak

-to

-peak am-

plitude

equal to the total

zener vol-

tage. Operating power

supplied by

batteries

B1 and 82 controlled

by a

dpst

switch,

Si.

Readily

available

standard compo-

nents

are used

the design. Ted

chose

type 741

op amp

for

ICI. The

terminal

numbers

shown

are for the

"minidip" version

used

in his

original

model.

The

resistors

may

be either 1/4

or 1/2

watt, while

is a low- voltage

ATTENTION

HOBBYISTS!

BUILD THIS

DIGITAL

COUNTER/

L.E.D.

DISPLAY

Everything

needed to

build a complete

decade

counter 09)

including

a printed

circuit

board.

Operates

from a 5

Volt D.C. supply.

Can

used

in hundreds

of applications.

See

your nearby CALECTRO

distributor

for all

the most

popular

digital

displays

and

integrated circuits.

Also,

get

your copy

of the

new

CALECTRO

DIGITAL

PROJECTS

HANDBOOK!

ELECTRONICS

Division of

Hydrometals,

Inc.

Rockford,

Illinois

61101 U.

.A..

ceramic

capacitor.

Batteries

81 and

82 are conventional 9 -volt transistor

units, with

a toggle,

slide or

rotary

switch.

Ideally,

the

zener diodes

should be matched,

with a total vol-

tage

volts. Unable

to obtain a

perfect match, Ted

assembled his

model

using

5.6 -volt

zener for

D1, a

4.5 volt

device for

D2, providing

nominal 10.1 -volt

output

signal.

The

actual output

voltage,

course, will

depend on

the zener diode

voltage

tolerances.

a particular application requires

an accurately

known output voltage, a

simple

test will establish this

value.

Disconnect

R4's

upper lead (pin 6,

ICi). Reverse D2. Connect R4's

free

lead to the

positive

terminal of a

-18 -volt dc source,

negative to

cir-

cuit ground.

Finally, measure the do

voltage across the series zeners using

an accurate

voltmeter.

Restore the

circuit to

its

original condition

for

normal

operation.

Device

/Product

News. We've re-

ceived a

number

inquiries from

readers

asking

what LED's have the

lowest

current

ratings. Actually, most

LED's

will operate at currents

much

lower than their maximum ratings,

and we've

obtained satisfactory

light

outputs with

levels

low

as 8 to

using commercial 50 -mA (max)

devices. However, the results

are

not

consistent. One

LED

a given type

may

provide a good output

at a

7 -mA

level,

while another of

the

same

type

may require 10 mA,

and still another

15 mA. At least

one

firm, however,

Data

Display

Products

(5428

104th

St.,

Los

Angeles, CA 90045),

offers

complete

LED panel -light

assemblies

designed to be used at a

mere

5 -mA

current

level. Available

colors are

green,

yellow,

amber and red, at vol-

tages from 1.8 to 28 V.

Single unit

prices range from

$1.58 for

1.8

-volt

device (requiring

an external current

limiting

resistor) to

$1.76

for

28 -volt

type

(with

built -in resistor). Each unit

supplied

with a

mounting

clip and

Neoprene washer.

You

can add another

name to the

roster of firms

manufacturing dual

555

-type timer IC's: Silicon General,

Inc. (2712

McGaw Ave., Irvine, CA

92705).

Packaged in

14 -pin DIPs,

the

Silicon General

version is identified

the SG556/SG556C.

Perhaps

dual timer is not

enough

for your application.

If this is the case,

you

might check

the new quad

timers

now

available

from

Signetics (811

Arques Ave., Sunnyvale, CA 94048).

Identified as

Models

553 and 554,

the

new units are supplied in a

-pin DIP.

The

553 and

554

are

not

exact dupli-

cates of

the industry

standard, the

familiar 555,

however. They

have no

reset control line and a common con-

trol

voltage

provided

for

all four

timers in the package.

Basically

simi-

lar in application, the 553 is rated to

sink

100 mA, the 554 to

source

equivalent current, compared to

the

200 mA ratings

the 555/556

types.

Another interesting difference

be-

tween the 553/554 devices

and the

555/556

types is a simplification

their timing equations,

from T = 1.1

T = RC for the new

units.

How many

watts in a dollar?

this

seems

a silly

question,

compara-

ble

mixing

apples and oranges,

it is, however, the type of

question

that

transmitter designer

must

ask him-

self.

According to

Motorola,

its new

MRF621

uhf

power transistor can de-

liver

an output

signal in

the

406 -to-

512 -MHz

band for less than

dollar

per

watt. Designed

for

12.5

-V

dc opera-

tion,

the new device can

deliver 45 W

470 MHz with

minimum

power

gain of

4.8

and collector efficien-

55 %. Featuring

an internal MOS

capacitor chip for "controlled

-Q"

operation,

the MRF621

sells for

$39.00 each in

unit

quantities,

even

less if you want to

buy

time.

RCA's

Solid State

Division (Box

3200, Somerville,

N.J. 08876) has in-

troduced a new linear

and

added

another

COS /MOS device to its

ex-

panding line.

Designated

type

CA3127E, the new linear device

con-

sists

of 5 independent general -

purpose

silicon

npn transistors

con-

structed on a common monolithic

substrate

provide close electrical

and

thermal matching.

Suitable for

low

-power applications at frequencies

500

MHz,

the CA3127E,

supplied

-lead plastic DIP,

can be used

vhf

amplifiers,

mixers

and oscillators,

in i -f

converters and amplifiers, and in

sense amplifiers, synthesizers, and

cascade amplifiers.

RCA's latest

COS /MOS device, identified as

the

CD4093AE, is a quad

2 -input NAND

gate consisting of

four identical

Schmitt trigger circuits, each

of which

functions as a two -input

NAND

gate.

The CD4093AE, packaged

14 -pin

plastic

DIP,

suitable

for

use in

wave

-shapers

and pulse- shapers,

mon-

ostable

and

astable

multivibrators,

and NAND

functional logic circuits.

POPULAR ELECTRONICS

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