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Noisy ac analysis result at low frequency

eyalg

When running ac analysis and plotting transfer function of amplifier I am getting noisy results at low frequency.

Its looks like accuracy of the simulator and when changing gmin it some times helps.

Is there a way to eliminate this noisy results?

  • eyalg

    When running ac analysis and plotting transfer function of amplifier I am getting noisy results at low frequency.

    Its looks like accuracy of the simulator and when changing gmin it some times helps.

    Is there a way to eliminate this noisy results?

  • Andrew Beckett

    I wouldn't expect that level of numerical noise, especially not when the gain is so high - that's rather strange. I also don't think that gmin would affect it, assuming that gmin is reasonable (near the default of 1e-12).

    Please contact customer support. This is rather unusual.

    Andrew

  • Frank Wiedmann
    in reply to Andrew Beckett

    We have seen this kind of problem rather often, usually on RLCK-extracted circuits, and currently have CCR 2470950 open for such a problem. In this case, plain Spectre could simulate the circuit just fine while APS had big problems.

  • Andrew Beckett
    in reply to mize
    mize said:
    i am wondering is this type of frequency the same as that of online radio or radio television?

    Huh?

  • Frank Wiedmann
    in reply to Andrew Beckett

    Seems like we have another case of link spam here...

  • Andrew Beckett
    in reply to Frank Wiedmann

    Frank - it wasn't a link when originally posted (I checked). I'll delete the item and ensure that the user is blocked. I do wonder why people bother!

    Andrew

  • Frank Wiedmann
    in reply to Frank Wiedmann

    You now might want to check if you get better results with SPECTRE 20.1 ISR13 or 21.1 ISR4 and later versions (see https://support.cadence.com/apex/ArticleAttachmentPortal?id=a1O3w000009favqEAA).

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