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[SOLVED] small signal-model Promblem. why does the dependent Current source dissappear?

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alexyangfox

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I saw this circuit in Razavi's book ——"Design of Analog CMOS integrated Circuits"
I don't understand his analysis.
the book says
the gain is:
52_1301226795.jpg

It seems when considering the Small signal model
the Dependent Current Sourse is gone.

I think it should be like this:
3_1301226847.jpg

Say , a quarter of the book's answer.


Could anyone help me with this puzzle?
Why is the dependent Source gone?
Or I made a mistake?
Thank all of you in advance!

best wishes to all guys here.
sincerly,
alex.
 

That is not the Current controlled current source. It is just a DC current ( iac=0)which its value is a fraction of M1's current to increase the gain.
 
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