exp
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Hi,
I have a simple diff pair setup where I add degeneration resistance Rs to the source:
In my opinion, the gain should become now gm/(gds*(1+gm*Rs)).
However, no matter which value of Rs I pick the output of the ac analysis always stays the same (roughly).
E.g., Rs=0: a0 = 80.2407, Rs=10k: a0 = 80.2374, Rs=1M: a0 = 79.9043 where a0 is taken from the output of the ac analysis.
The same happens if I set a constant input voltage and see the output voltage with .dc analysis.
This is crazy, absolutely impossible!
Is there an obvious mistake?
I have a simple diff pair setup where I add degeneration resistance Rs to the source:
In my opinion, the gain should become now gm/(gds*(1+gm*Rs)).
However, no matter which value of Rs I pick the output of the ac analysis always stays the same (roughly).
E.g., Rs=0: a0 = 80.2407, Rs=10k: a0 = 80.2374, Rs=1M: a0 = 79.9043 where a0 is taken from the output of the ac analysis.
The same happens if I set a constant input voltage and see the output voltage with .dc analysis.
This is crazy, absolutely impossible!
Is there an obvious mistake?