Variation in the operating frequency of an op-amp causes variations in both the gain amplitude and the phase angle of the output signal. This is known as frequency-dependent behavior.
Frequency Response Effects:
At different operating frequencies, the op-amp shows different gains and phase shifts. The open-loop gain decreases at higher frequencies due to internal frequency compensation. This creates a trade-off between bandwidth and gain.
Phase Shift:
As frequency increases, the phase shift between input and output also increases. This is due to the capacitive elements within the op-amp circuit affecting the signal propagation.
The correct answer is typically: (c) Variation in gain amplitude and its phase angle
This comprehensive answer captures the complete frequency response behavior of op-amps. Both magnitude and phase characteristics change with frequency, which is critical in understanding op-amp performance in AC circuits and frequency-dependent applications.