Dear all,

I have a question about loop analysis, hope anyone can help me. Thank you very much!

I want to break a close-loop circuit to perfrom stability analysis (gain & phase margin) now. Normally, i should break the node where is the high impedance point (e.g. between OTA's output and input).

But the node that i want to break is between Drain of M1 and Source of M2. If i break it and insert inductor, capacitor and ac-source into it, the couple effect between drain and source is ignore. So, what can i do?

I had tried to duplicated the M2 and connect it to M1 in parallel, so that Drain of M0 can still see the source of M2, but Ids in M0 is double. Seems not correct, right?

Please help me! Thanks!

Best Regards,
George

Thank you for your reply!

Here is the diagram of the circuit. acutally, it is a circuit in paper "AREA-EFFICIENT LINEAR REGULATOR WITH ULTRA-FAST LOAD REGULATION"


I perform an analysis as follow:

In this setting, the couple effect of M0 drain and M4 source is ignore.

So, it is modified as follow:

But the Ids of M0 is doubled!
So, how can i do? Thank you!