Poles and zeros of two stage miller compensated opamp

[katarisrinu786]

I am trying to design a two stage miller compensated opamp with nmos input pair. I am unable to figure out the expressions for the poles and zero locations.
I mean simulation values (pole, zero locations) not matching with the conventional expressions except for the zero location (due to RZ) and dominant pole location.
Can some one help me out here ?. Especially for first non dominant pole location ?.

 

[Dominik Przyborowski]

What you called conventional expression is probably open loop transfer function, while you are calculating closed loop case.

 

[katarisrinu786]

What you called conventional expression is probably open loop transfer function, while you are calculating closed loop case.

Hi sir,
You are right. I am unable to calculate poles and zeros in closed loop. In open loop they are fine.

 

[Dominik Przyborowski]

So, the question is what do you want to achieve? If your goal is to check stability, then you should calculate signal at the end of loop (voltage on Rf) with grounded noninverting input of your 1st transconductor.
However, if your goal is to calculate transfer function of closed loop system, does not expect the same results as for open loop bare Amplifier.