Page 81 - Electrician - TT (Volume 2)

ELECTRICIAN - CITS

Fig 1 Fig 2

The most popular three terminal IC regulators are,
1 LMXXX-X series

Example: LM320-5, LM320-24 etc.
2 78XX and 79XX series
Example: 7805, 7812, 7912 etc.
A list of popular three terminal regulators is given in IC data book.

Specifications of three terminal IC regulators: For simplicity in understanding, let us consider the specification
of a three terminal IC µA7812. The table 2 given below lists the specifications of µA7812.
Table 2
Parameter Min. Type. Max. Units

Output voltage 11.5 12 12.5 V
Output regulation 4 120 mV
Short-circuit
output current 350 mA
Drop out voltage 2.0 V
Ripple rejection 55 71 dB

Peak output 2.2 A
current

Identification of output voltage and rated maximum load current from IC type number
– 78XX and 79XX series are 3 Terminal voltage regulators.
– All 78XX series are positive output voltage regulators
– All 79XX series are negative output voltage regulators
The term XX indicates the rated output regulated voltage.
Example
7805
Indicates positive Indicates output
output regulator voltage is +5V
7912
Indicates negative Indicates output
output regulator voltage is –12V

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