CMFB design help for the class AB output stage current mirror OTA

[Junus2012]

Dear friend

I am designing a fully differential amplifier for the first time. I would design the CMFB for the OTA shown in image below

I would use continuous time CMFB, while all the references I have only discussed the SC CMFB for this circuit. If any one can help me I will be thankful for him

Enjoy

 

[erikl]

I would use continuous time CMFB

Something like this:

For R0, R1 use order of MΩ; C1, C2 tenths of pF; C0 only if stability pb.

 

[Junus2012]

Thank you erikl

But actually I dont want to use the resistors in my design since it take a lot of space and I am not intending to design a buffer for driving the small one . rather I would like to use the Differential CMFB shown in the image below but my problem I dont know wherew should I connect the F.B signal with this OTA circuit

Thanx again

 

[erikl]

Vcmc (common mode control) is the F.B. output. Connect it to both CMFB inputs of your OTA.

 

[prcken]

hi, but i think for the class AB output stage this kind of CMFB is not good, it has the linearity problem at large signal swings, I prefer to use resistive one for continous time output stage CMFB.
can you tell me which paper is that talks about SC-CMFB for class AB output stage? i think it's very hard to get high CMFB gain for that 2nd stage to use SC CMFB.
thanks!