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  1. #1
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    Constant-gm bias circuit

    For https://designers-guide.org/forum/At...amp.pdf#page=3 , how to derive expression (14) ?

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  2. #2
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    Re: Constant-gm bias circuit

    Do you guys know how to come up with the equation for RDS4C ?




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  3. #3
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    Re: Constant-gm bias circuit

    I got a different answer, maybe I made a mistake in the derivation but you can check to see if it's right though.
    Click image for larger version. 

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    edit:
    Oh I see my mistake now, when I absorbed (W/L)4c into the square root I forgot to square it. and (W/L)4c=P/M * (W/L)2E which would make
    Rds=[2uCox(P/M)^2(W/L)2E*ID]^-1/2 which would equate to gm2E^-1/2 * M/P
    Last edited by rmanalo; 6th May 2019 at 10:07.


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  4. #4
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    Re: Constant-gm bias circuit

    Thanks. Could you rewrite the correct solution ?

    I am having problem following your derivation (with mistake).



  5. #5
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    Re: Constant-gm bias circuit

    If I made any mistakes, please point them out. Thanks.

    Click image for larger version. 

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  6. #6
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    Re: Constant-gm bias circuit

    Besides P, the M should have been squared inside the square root. I think you forgot it.

    I do not understand why gm4e is always independent of process, temperature and load variations ?



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