spectre PSS/Pnoise on Sampling & Hold Circuit

Discussion in 'Cadence' started by hb_huang, Jan 17, 2007.

  1. hb_huang

    hb_huang Guest

    I have run a PSS/Pnoise analysis for my sampling & hold circuit. The
    structure of circuit is switched capacitor, flip around with a
    gain-boosted amplifier. When printing noise summary, I found the top 8
    noise contributers (they generated 70% of total noise) are not from
    main amplifier, but from gain boost amplifier (AUX amplifier). It's
    pretty much way out of my imagination, the noisy amplifier is on the
    signal loop though. My PSS/Pnoise setting up are like following:

    PSS: 80M beat frequency, number harmonics: 20; time of stable: 300n,
    maxacfreq: 1.6G
    Pnoise: start: 1, stop: 40M (Nyquist); Max Sideband: 20; Timedomain:
    time point 7.1n (hold end point)

    To interpret the Pnoise results, I did a noise analysis with a linear
    test bench for amplifier (main amplifier with AUX one) only, there most
    noise contributers are input and current soure transistors at main
    amplifier. It's very interesting that AUX amplifier has shown almost
    nothing with total noise this time. Does anyone has any idea with it?
    Thanks a lot.


    Regards

    Vincent
     
    hb_huang, Jan 17, 2007
    #1
  2. hb_huang

    Poojan Wagh Guest

    Could you give more definition on what you mean by "gain-boosted
    amplifier"? Do you mean an amplifier employing a gain-boosted cascode
    device?
     
    Poojan Wagh, Jan 18, 2007
    #2
  3. I think it's quite difficult to know what the problem is (assuming there is a
    problem) from just your very high level description of the circuit (I can't
    picture what it looks like from your description, for example). Probably the
    thing to do is to contact Cadence customer support with your testcase, and an AE
    can help you interpret the results.

    Best Regards,

    Andrew.
     
    Andrew Beckett, Jan 18, 2007
    #3
  4. hb_huang

    hb_huang Guest

    Thanks Poojan. My circuit is a quite typical folded cascode amplifier
    with pmos input. There are two AUX amplifiers working as gain booster
    on cascode NMOS and PMOS, respectively.

    There are several questions I want to figure out:

    1. If I can count on PSS/PNoise analysis for the noise estimation?
    Considering my circuit is working as switched capacitor way, looks like
    I don't have so many choices to get noise info. Also, this circuit is a
    Sampling & hold frount end stage for pipeline A/D, the next stage is
    working as switched capacitor circuit too.
    2. Is it correct that I choose "timedomain" within PNoise analysis? and
    time point (for timedomain analysis) is same as S/H's holding end point
    ? should I change it to other kind of noise format within PNoise
    analysis, like modulation, jitter or source?
    3. In this case, what's the physical meaning of PNoise's output? Is it
    really represent noise within this system?


    Regards


    Vincent

    "Poojan Wagh дµÀ£º
    "
     
    hb_huang, Jan 18, 2007
    #4
  5. I'd suggest reading:

    http://www.designers-guide.org/Analysis/sc-filters.pdf

    the netlists are available at:

    http://www.designers-guide.org/Analysis/sc-netlists.zip

    if you need them.

    This is a good overview of using SpectreRF to simulate switch cap circuits, and
    will probably answer your questions.

    Regards,

    Andrew.
     
    Andrew Beckett, Jan 24, 2007
    #5
Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.