Page 21 - Semester-IV-Electronics
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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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