How can improve CMFB GBW?

[castrader]

In my design of 2-stage class AB fully differential OP, ac gbw=25MHz av0=110dB
my cmfb gbw is only 5MHz av0=100dB
I use resistor as cm sensor, and use differential op with diode load as cmfb gain stage, feedback to class AB 1st stage tail current partly.
How to increase CMFB GBW?

 

[paley]

it's difficult that making the unity-gain freq of the differential-mode and CMFB loop about equal, because the cmfb loop have more poles than DM loop

 

[Alan_Nesta]

maybe you can try another cmfb, like feedback to the load device of the first stage, maybe it is useful.