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input and output noise simulation with Spectre Noise analysis?

isazulkc
Hi, I would like to know if the output noise (V-rms) obtained when I simulate the output noise of a circuit with Spectre simulator (Noise) include the noise of ALL the components referred to the output ? In fact I got some inconsistant result when comparing the input and output noise (V-rms) given by the simulator. I got 1.4 mV-rms at the output while I have 13 mV-rms as input refered noise. I know input referred noise give the input equivalent noise (anasimhelp) considering a noise-free circuit, but I am note sure for the output noise. Thanks for your help!! Best regards
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  • Andrew Beckett

    Posting on the end of an old thread clearly didn't get a quick answer - I don't know why you did this (the forum guidelines explain why you shouldn't)?

    1. There's no need to create an iprobe, since to compute input referred noise, you need to specify the input source - which can be a current source. In fact I don't think it would work with a noise analysis anyway to use the iprobe.
    2. You should specify your noise analysis in spectre syntax:
      noise (out 0) noise start=1 stop=1G dec=10 iprobe=Idriver
    3. Just add isnoisy=no on the end of the Rfb line. Personally I wouldn't mix spectre and SPICE syntax, but it does work fine in this case.

    Your transistors don't have model names or sizes defined, but I assume this is just to illustrate what you're doing.

    For pnoise, you'd have to also set up a pss analysis too. Look at "spectre -h pss" and "spectre -h pnoise" for details on using these analyses. Or for some command line examples, you could look at: Simulating switched-capacitor filters with SpectreRF

    Regards,

    Andrew

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  • Andrew Beckett

    Posting on the end of an old thread clearly didn't get a quick answer - I don't know why you did this (the forum guidelines explain why you shouldn't)?

    1. There's no need to create an iprobe, since to compute input referred noise, you need to specify the input source - which can be a current source. In fact I don't think it would work with a noise analysis anyway to use the iprobe.
    2. You should specify your noise analysis in spectre syntax:
      noise (out 0) noise start=1 stop=1G dec=10 iprobe=Idriver
    3. Just add isnoisy=no on the end of the Rfb line. Personally I wouldn't mix spectre and SPICE syntax, but it does work fine in this case.

    Your transistors don't have model names or sizes defined, but I assume this is just to illustrate what you're doing.

    For pnoise, you'd have to also set up a pss analysis too. Look at "spectre -h pss" and "spectre -h pnoise" for details on using these analyses. Or for some command line examples, you could look at: Simulating switched-capacitor filters with SpectreRF

    Regards,

    Andrew

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