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instrumentation amplifier & anti-aliasing

Discussion in 'Electronic Components' started by Ponkan, Jul 24, 2003.

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  1. Ponkan

    Ponkan Guest

    Hi,
    I was wondering if I could "integrate" easily a low-pass filter (for
    ADC anti-aliasing purpose) in an instrumentation amplifier.
    I would not want to include an active filter between the
    instrumentation amplifier (the ADC buffer) and the ADC itself. Just
    wanted to use to the instrumentation amplifier to do the job. Any
    idea? For the instrumentation amplifier I was thinking of the
    Burr-Brown INA128 and for the ADC the Burr-Brown ADS7813. The ADC can
    work at up to 40kHz and I would like to limit the input bandwidth to
    10kHz. Maybe a simple RC between them is enough... I would like to see
    your points of view.
     
  2. Bob Masta

    Bob Masta Guest

    The main point of using an instrumentation amplifier is that it
    has differential inputs with good common mode rejection.
    If you try to turn a differential input into part of a filter, you
    will almost certainly mess up the common mode rejection,
    not to mention needing extra parts for each input. Why not
    just use a separate op-amp filter stage?

    Also, depending on exactly what you are using the ADC
    for, you may be better off not using any filter at all.
    You need a filter if you want to be able to handle any
    arbitrary input without aliasing, but I have found that
    there are huge numbers of applications where this
    isn't really needed. And if it *is* really needed, it
    usually needs something a whole lot beefier that
    the simple few poles you are likely to want to build
    yourself.

    Tell us about your application and we may be able
    to give specific advice.


    Bob Masta
    dqatechATdaqartaDOTcom

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    Shareware from Interstellar Research
    www.daqarta.com
     
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