How to obtain the poles and zeros of loop gain in PZ simulation

Hello, I am a junior engineer.

I am running both STB and PZ simulations to analyze how the phase margin changes depending on the presence or absence of a Miller capacitor, and more specifically, how the pole locations shift.

To obtain the poles and zeros of the loop gain using PZ simulation, I broke the loop, applied the DC voltage obtained from a DC simulation using a VDC source, and then ran the PZ simulation. However, the pole/zero values and the DC gain I obtained were different from the loop gain results from the STB simulation.

I would appreciate your advice on how to interpret this difference. Is there a correct or standard way to accurately obtain the poles and zeros of the loop gain? Or is my approach fundamentally incorrect?

Any comments or suggestions would be greatly appreciated.

(I’d like to attach a photo, but it won’t upload.)