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MOSFET Differential Pair Behavior

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작성자 Anonymous 댓글 2건 조회 540회 작성일 20-06-22 00:10

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Hello, I am quite confused with the behavior of differential pair for a MOSFET. I tried modelling it in PSPICE to understand it better as shown in the schematic attached. However, the output voltage seems to be slightly distorted compared to the input (it doesn't seem like a smooth sine curve).

1) Is this correct differential pair behavior? If so, why is the output curve slightly distorted?

I used the MbreakN and MbreakP models to eliminate any non-idealities.

2) Also, is there a way to calculate the gain of this differential pair circuit if lambda = 0 (ro = infinity)?
It seems like the calculations done in class all used non infinite ro. Does that mean infinite ro will lead to infinite output impedance => infinite gain?

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Anonymous 작성일

Your input voltage swing is 1V, too large.
Your supply voltage is only 3.3V and if your diff amp gain is more than 3, your output signal will be distorted like your picture.
1. Reduce the input voltage swing or
2. Reduce voltage gain of your diff amp

Anonymous님의 댓글의 댓글

Anonymous 작성일

Do you know how to calculate/change the gain if lambda = 0 is constant?

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