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sampled pnoise on multi-phase switched cap circuit

jfyan

Hi,
I have one question about the sampled pnoise simulation:
If I have a switched capacitor sample and hold circuit to sample the noise of resistor R, and now I add another switch sampler just paralleled with the first switch, with same sampling freq (fs) but nonoverlapping. so, the pss fund. freq = fs, but essentially the switch freq is 2fs.

how can  I simulate the circuit to get the right noise density (4kTR*pi/2*f3db/fs), instead of 4kTR*pi/2*f3db*2/fs? is pnoise option "sampleratio" is right way to do here.

thanks
Jeff

Parents

  • Dear jfyan,

    jfyan said:
    If I have a switched capacitor sample and hold circuit to sample the noise of resistor R, and now I add another switch sampler just paralleled with the first switch, with same sampling freq (fs) but nonoverlapping. so, the pss fund. freq = fs, but essentially the switch freq is 2fs.

    I do not believe your switch frequency is 2fs with the introduction of a second parallel switch whose phase only differs from the first parallel switch. The switch frequencies, and hence pss analysis, is still at fs and not at 2fs.

    Shawn

  • in reply to ShawnLogan

    Hi Shawn

    yes, that is the problem, the pss fund. freq can only be set at fs, not 2fs. but essentially the resistor noise is updated at two fs. here, for example, these two clocks are 25% duty cycle, and half 1/fs away from each other.

    regards,

    Jeff  

Reply
  • in reply to ShawnLogan

    Hi Shawn

    yes, that is the problem, the pss fund. freq can only be set at fs, not 2fs. but essentially the resistor noise is updated at two fs. here, for example, these two clocks are 25% duty cycle, and half 1/fs away from each other.

    regards,

    Jeff  

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