raja.cedt wrote on Sep 1st, 2011, 3:36am:hello nrk1,
thanks for your note. ya i forgot this. But from erlier post gain from gate of m1 is zero but one thing is m2 gate also moves due to m4,m3, correct me if am wrong.
Thanks.
Ya you may be right.
1st look left side arm :- due to del-V increment at the gate it will cause del-I1 current sink at the +ve Node of the OPAMP. So del-V1 reduction in + Node of the OPMAP.
2nd look right side arm:- due to del-v increment at the gate it will cause let say del-I2. But this will be far far smaller than del-I1 as it is degenerated by a current source M3. However due to the current mirror action of the left side ( you can apply supperposition for better understanding) del-I3 current will flow FROM the -ve Node. Now question is whether de-I3+del-I2 > or < del-I1. If > then it is a POSITIVE feed-back. If < then it is a NEGATIVE feedback. If the component generated due to mirroring action del-I3 is quite smaller than del-I1 then you will END up getting NEGATIVE feedback.
Ricky-
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