Page 81 - Electrician - TT (Volume 2)
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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
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