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Design >> Analog Design >> nonlinearity of cascode MOS straucture
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Message started by xuedashun on Apr 14^th, 2010, 11:52am

Title: nonlinearity of cascode MOS straucture
Post by xuedashun on Apr 14^th, 2010, 11:52am

I got this interview question and am not sure what's the exact answer.
Could you give some suggestion? Thank you.

For the normal cascode CMOS structure, which contribute to more nonlinearity?

Title: Re: nonlinearity of cascode MOS straucture
Post by aaron_do on Apr 14^th, 2010, 5:41pm

Hi,

If you are talking low frequencies, ideally the cascode MOS doesn't contribute to the nonlinearity since I_out,M1 = I_out,M2 where M₁ is the input transistor and M₂ is the cascode. That's my understanding anyway.

At high frequencies (RF) the above equation doesn't hold due to the capacitances at the interconnecting node.

cheers,
Aaron