What is the role of a compensating capacitor in a Miller integrator to improve stability?

• A. It increases the op-amp's high-frequency gain to extend bandwidth.
• B. It creates a dominant pole by feeding back high-frequency signals, reducing the op-amp's high-frequency gain and improving phase margin.
• C. It eliminates all poles in the feedback loop.
• D. It short-circuits the input to ground at high frequency.

Answer: (B)

The main idea is to shape the loop gain so the system has a single, low-frequency dominant pole that governs the response, which keeps the phase shift under control and prevents instability. The compensating capacitor across the feedback path feeds high-frequency signals from the output back to the input. At high frequencies, this feedback becomes strong, which reduces the op-amp’s effective high-frequency gain and places a dominant pole in the closed-loop response. That lowers the overall bandwidth a bit, but it greatly improves phase margin, making the Miller integrator stable.

The other options don’t fit because boosting high-frequency gain would worsen stability, not improve it; eliminating all poles isn’t possible and isn’t how stability is achieved; and short-circuiting the input to ground at high frequency is not what the capacitor does in this configuration.