common mode feedback

for common mode feedback circuit stability ,need what conditions ,how to
tune the circuit to satisfy the conditions
thank you very much ,I am a tenderfoot for here ,wish help each others.

you should simulation the phase margin of CMFB circuit, commonly saying, Phase margin>60 degree

if phase margin <60,wether the circuit must be unstable,can you detail
the defination about phase margin.

thank you!