Page 21 - Semester-IV-Electronics
P. 21

 It has two input terminals = One output terminal + A ground

                 terminal, which is coupled to all the three other terminals.



             1 and 2 are input terminals and O is output terminal.



             The minus sign at terminal 1 means that for an input signal at this

                 terminal, the polarity of output signal is reversed, for this input the


                 amplifier generates a phase change of 180°. Hence, it is called

                 inverting input terminal.



             The positive sign at terminal 2 means that for an input signal at this

                 terminal, there is no change in polarity of output signal. Thus, the

                 phases of input voltage at 2 and output voltage at O remains the

                 same. This terminal 2 is called non-inverting input terminal.



             The output voltage at terminal O is proportional to the difference of

                 input voltages applied at terminals 1 and 2, i.e.,



             v α (v – v ) or v = A(v – v )
                                      1
                                                 0
                                                              2
                             2
                                                                      1
                    0
             Here, the proportionality constant A is called voltage gain of OP-
                 AMP.

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