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

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Junus2012

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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
 

Junus2012

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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

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

prcken

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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!
 
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