Page 21 - Semester-IV-Electronics

 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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