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PSpice Noise Analysis

Discussion in 'CAD' started by Bob Penoyer, Nov 19, 2003.

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  1. Bob Penoyer

    Bob Penoyer Guest

    I'm somewhat new to PSpice. One apparent feature is Noise Analysis.
    When I invoke this function, a couple of new terms appear in the left
    pane of the Add Traces window in Schematic. For my particular circuit,
    these are NTOT(ONOISE), NTOT(R1), NTOT(R6), V(INOISE), and V(ONOISE).

    I assume INOISE is input noise and ONOISE is output noise. They appear
    to give a noise profile as a function of frequency but what, exactly,
    are INOISE and ONOISE? Are they used separately? Should I use their

    A key question: Is there a direct way to make PSpice calculate the
    total rms voltage or current noise referenced to the input?
  2. No. They are the effective input/rthz and output noise/rthz, as you
    I don't remeber much about PSpice, now but I would guess that NTOT might
    be total noise;-)

    Now if you were using SuperSpice,,which is much
    more affordable an easier to use, I could help you more.

    Kevin Aylward
    SuperSpice, a very affordable Mixed-Mode
    Windows Simulator with Schematic Capture,
    Waveform Display, FFT's and Filter Design.

    Understanding, is itself an emotion, i.e. a feeling.
    Emotions or feelings can only be "understood" by
    consciousness. "Understanding" consciousness can
    therefore only be understood by consciousness itself,
    therefore the "hard problem" of consciousness, is
    intrinsically unsolvable.

    Physics is proven incomplete, that is, no
    understanding of the parts of a system can
    explain all aspects of the whole of such system.
  3. qrk

    qrk Guest

    INOISE = equivalent noise of total circuit, referenced to the input
    ONOISE = equivalent noise of total circuit, referenced to the output
    NTOT = total noise, used mostly for device noise. See PSpice help for
    "Device noise variables" for more noise info.

    In AC analysis, you set up the input source and output node as well as
    enable the noise reporting.

    The answer to your "key question" is yes. INOISE and ONOISE calculate
    the total circuit noise.

  4. Jim Thompson

    Jim Thompson Guest

    Yes, Mark, we *do* know a lot about noise ;-)

    ...Jim Thompson
  5. Bob Penoyer

    Bob Penoyer Guest

    Two follow-up questions:

    1. Do INOISE and ONOISE include the noise effects of components listed
    as arguments of NTOT? That is, if there are resistors connected in an
    op-amp circuit, for example, do INOISE and ONOISE include the combined
    effects of the resistors and the op-amp?
    2. Is there a way to convert the spectral profiles of INOISE and
    ONOISE to the total noise, that is, integrate INOISE or ONOISE over
    the swept frequency spectrum?
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