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help me calculate the CMFB gain

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shilpashetty

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hello
can you help me calculate the gain of the cmfb
here is the schematic

im1.png

and the author gives the following gain:

im2.png

i understand the 2gm6/(1+gm6R5), thats the current which is mirrored up to node B, then from node B on i am lost, how the current at node B is converted into a voltage vocm' :oops:

many thanks in advance

- - - Updated - - -

i made some progress, at node B, the impedance seen is ~ 1/gm4, then this voltage is multiplied by the cascode gain which is equal to gm4/goc which yields the same formula as the author .
however in the goc formula i dont see from where comes the term 2 , for me there is no 2 :?:
 
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