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  1. #1
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    Analog Layout - Multipliers and Fingers

    Hello,

    For Analog Mixed Signal Layout in CMOS in 65nm and blow, what finger size and multiplier should be used ?

    I have been told to avoid multipliers unless in cases of Common Centroid layout.

    Also, what finger size to pick ?

    Someone recommended to me W < 20 ∗ L at lower or at 65nm CMOS for the size of each finger (so for 65nm - thats 1.3um per finger - seems low).

    Should one avoid multipliers ?

    Should one use both multipliers and fingers ?

    What is the finger size rule ?

    What other considerations are there ?

    Thanks.
    Last edited by Puppet123; 21st June 2019 at 02:45.

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  2. #2
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    Re: Analog Layout - Multipliers and Fingers

    Gate resistance is a key concern for RF and very high
    speed drivers.

    Debiasing effects matter at higher currents, if you feed
    one end through skinny metal the far end may not "pull
    its weight" or match well.

    Electromigration can be a problem if high DC current is
    wanted / rated, you need enough total metal width to
    meet EM rules (or be sure to feed the S/D in a better
    way)

    There are probably limits in the design kit that stop you
    from using Wfinger values beyond what has been
    characterized / modeled / qualified. You might peer at
    the device characterization / modeling documents and
    avoid anything that seems "off the map".



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