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  1. #1
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    Bipolar circuit schematic has no size specified.

    In MOS circuit schematic, it specifies the W/L size but Bipolar schematic, it doesn't specify the size. How do I know the size of the emitter, collector?

    •   Alt20th February 2018, 02:04

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  2. #2
    Advanced Member level 5
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    Re: Bipolar circuit schematic has no size specified.

    Maybe they do not want you to know. Device sizing
    is part of the art and has to balance multiple interests
    (for example, is your Vio hurt more by minimum emitter
    area (raw matching) or by gain reduction (hFE-vs-Ic,
    reduced "attenuation of back end systematic offset")
    given that you want to run the front end at minimum
    current so as to make Iib spec?

    It's in nobody's interest to help you knock off their
    part, so you never, as far back as I've ever seen
    (and I have quite a collection) find datasheet schematics
    showing such detail. Maybe resistor values if the MarCom
    people were less than diligent (or their department did
    not yet exist, at publication).

    As a rough approach I recommend assuming they are all
    minimum, and then do the work to figure out better sizing
    based on what your analysis shows you. Because absent
    other interests, die area is still concern #1.



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