I'm studying cascode mirror and i have a question about: there is a feedback in this circuit? For example, if i consider this picture:
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I1 is costant, so in the small signal analysis M1 and M3 gates are grounded. But, following the same procedure used to explain feedback in wilson mirror, if i change Idm4, Vgsm2 also changes. Vgsm2 is egual to Vgsm1 so current in M1 changes: so Vg1 isn't grounded in small signal analysis. What's wrong?