Page 82 - Electrician - TT (Volume 2)

ELECTRICIAN - CITS

It is important to note that, different manufacturers of 78 XX/ 79XX series such as Fair Child (MA/Mpc), Motorola,
Signetics (SS) adopt slightly different coding schemes to indicate the rated maximum current of the three pin
regulated. ICs. One such scheme is given below.

78LXX - L indicates rated maximum load current as 100mA.
78MXX - M indicates rated a maximum load current as 500mA

78XX - Absence of an alphabet between 78 and XX indicates that the rated maximum load
current is 1A.

78SXX - S indicates rated maximum load current is 2amp.
Example
µPC 78 M 15H
Indicates positive Indicates

Fair Child Regulated output
(Manufacturer’s voltage is 15V
code)
Positive regulator Rated maximum
load current is
500mA

LM 3XX series of 3 terminal voltage regulators: In LM series of three terminal regulators, to find the specifications,
it is suggested to refer to its data manual. However, the following tips will help in identifying whether the IC is a
fixed positive or fixed negative regulator.

LM320-X and LM320-XX  Fixed –ve voltage

regulators.

LM340-X or LM340-XX  Fixed +ve voltage

regulators.
Examples
LM 320 - 5

RCA Output
(Manufacturer) voltage -5V
Fixed negative
voltage regulator
LM 340 - 15
RCA Output

Fixed positive
voltage regulator

69

CITS : Power - Electrician & Wireman - Lesson 60-69