input-referred port noise

Discussion in 'Cadence' started by Jack, Feb 19, 2006.

  1. Jack

    Jack Guest

    Hi,
    I am doing spectre noise analysis and I am expecting the input-referred
    noise power of a power to be just 4kTR, where R is the port impedance.
    However, I keep getting kTR, which is 1/4 of what I expect. Can anybody
    help explain why?
    Thanks.

    Best,
    Jack
     
    Jack, Feb 19, 2006
    #1
  2. Jack

    Andrew Beckett Guest

    Jack,

    The input referred noise is referred back to the source within the port - and so
    it might be something to do with the voltage gain factor of 2 on that internal
    voltage source - that gain factor is there to ensure that if the port drives a
    matched load, it give the correct signal level at the output of the port. If
    driving a high impedance load, it will generate double the signal level.

    If you have access to http://sourcelink.cadence.com you may want to look
    at solution 11025268 which gives a worked example of nise analysis.

    Regards,

    Andrew.
     
    Andrew Beckett, Feb 21, 2006
    #2
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