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Voltage jump in transient noise simulation when reading data from file

thegon

Dear all,

I want to include a voltage noise source with a custom spectrum given in a file in a transient noise simulation. For illustration purposes, I made a minimal example as shown below. It merely contains a "vdc" source from "AnalogLib" with "vdc=0V", where a very simple noise data file containing just three points is entered.

As can be seen in the noise simulation at the upper right, the data seems to be interpreted correctly. However, when I run a transient noise simulation with 1ms duration (see its setup in the image), there seem to be jumps in the order of tens of millivolt at the very beginning that remain a "dc offset" during the whole simulation time. I am using the Cadence Spectre simulator, but APS returns the same results.

I did not expect this behavior, I rather expected my noise sources to have an average of 0V during each 1ms-run. Am I overlooking something, or what is going on here?

Thank you!

Best regards,
thegon

  • Dear thegon,

    thegon said:

    However, when I run a transient noise simulation with 1ms duration (see its setup in the image), there seem to be jumps in the order of tens of millivolt at the very beginning that remain a "dc offset" during the whole simulation time. I am using the Cadence Spectre simulator, but APS returns the same results.

    I did not expect this behavior, I rather expected my noise sources to have an average of 0V during each 1ms-run. Am I overlooking something, or what is going on here?

    I was piqued by your question as I have recently done a lot of simulation work and subsequent analysis using the Transient noise option of Spectre. Hence, I tried to duplicate your results. I've placed a summary of my attempt at URL:

    https://www.dropbox.com/s/mgw8oe7yakbh11y/test_vnoise_from_file_example_080822v1p0.pdf?dl=0

    If you might compare your input.scs and netlist files with those I included on pages 2 and 3, it might provide some insight into why your results are not as you expect. Otherwise, might you allow us to view your netlist, input.scs file, and tool versions? I think with this information, I could provide some added thoughts thegon.

    Shawn

  • in reply to ShawnLogan

    Thank you so much ShawnLogan for taking the time and having a look! So far, I compared the netlists but could not spot anything obvious and my problem persists, but its good to see that it works in principle. At the moment, I do not have time, but I will have a closer look come back to it here.

    thegon

  • in reply to thegon

    Dear thegon,

    thegon said:
    t the moment, I do not have time, but I will have a closer look come back to it here.

    I fully understand how time can be an issue! If you do happen to have time and it is not proprietary, if you upload your input.scs, netlist, and spectre.out file, I'd be happy to take a look. Once again, please only consider this if you have time - I don't want to interrupt your busy schedule and prevent you from addressing more pressing issues!

    Shawn

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