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The output impedance of a non-ideal operational amplifier is denoted by Z_out. The variation in the magnitude of Z_out with increasing frequency, f, in the circuit shown below, is best represented by

1. (A) log(|Z_out|) versus log(f) is a horizontal line
2. (B) log(|Z_out|) versus log(f) is a straight line with positive slope
3. (C) log(|Z_out|) versus log(f) is low at first, then increases to a higher constant value
4. (D)

Correct answer: (C) log(|Z_out|) versus log(f) is low at first, then increases to a higher constant value

Solution

The correct option indicates that as frequency increases, the output impedance initially remains low due to the operational amplifier's feedback mechanisms, but eventually rises to a higher constant value as the effects of parasitic capacitances and other frequency-dependent factors become significant.

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