Page 29 - Semester-IV-Electronics

Input Offset Current

 If no voltage or equal voltage is applied on the input terminals of

a differential amplifier of OP-AMP, then, in ideal state the

output voltage must be zero, V = 0 if V = V or V = V = 0.
0 1 2 1 2

 In practice, due to mismatch of transistors or imbalance of input

signal voltages or defects in fabrication, the output voltage is not

zero when the input voltages are zero or equal.

 Due to certain reasons, the direct current I and I at the two
1 2
input terminals are not equal inspite of being very small i.e. for

zero input, the output voltage does not become zero.

 This difference in biasing current is called input offset current.

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