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noise quuestion - µV vs nV sqrt(hz) ?

Discussion in 'General Electronics' started by leye, Feb 9, 2004.

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  1. leye

    leye Guest

    How does one compare noise figures expressed in µV v.s. more famillar
    nV SQRT(Hz) ?

    More precisely, if MAX412 has 2.2 nV SQRT(Hz) and NJM2068 0.56µV -
    which one is noiser under same conditions (frequency, impedance,
    temerature, etc).


  2. Robert Baer

    Robert Baer Guest

    If the noise of a device is speced in uV and another specd in
    nV/rootHz, thenone must beconverted to the other by applying the same
    bandwidth criteria.
    For example, the uV spec should have a bandwidth stated or speced, so
    nV/rootHz could be calculated.
    Likewise, one might be able to correctly apply that bandwidth to the
    nV/rootHz spec and calculate the total noise.
    That takes care of the frequency part you asked about.
    Impedance (of the source) is a totally different aspect and may or may
    not be defined.
    And nobody has ever specified noise at a temperature other than room
    temperature, so that aspect cannot be relevant.
  3. leye

    leye Guest

    Well, depends who defines it, ISO says 18deg C, most manufacturers 20.
    Then, impedance 50, 75 or 110 ohm. When expressed in µV some bandwidth
    curves tend to be quite exotic - just pointing out how hard is to
    compare anything when manufacturers chose methods that flatter the
    Guess it would be easier just to put ICs in the socket and A/B them.

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