Disto simulation with BSIM4

  • Anonymous - 2012-04-22

    I'm trying to run a disto simulation on a circuit containing mosfets with BSIM4 level 54 model.
    For some reason, I only get 0's for the 2nd and 3rd harmonics. I was wondering if anybody has been running into the same problem. I don't get any errors though and it generates a result file containing all zeros for my output nodes. I'm just wondering if this is a known issue. I tried running the simulation on a circuit containing BJT's and it worked fine.
    I appreciate any help.
    Thank you.

  • Dietmar Warning

    Dietmar Warning - 2012-04-22

    Hi Nima,
    can you provide us a simple testbench including the model which you have used.
    Did you try other models like BSIM3v3 or level 8?

  • Anonymous - 2012-04-22

    Hi Dietmar,
    Thanks for replying. I have a simple example and I'm using the built-in BSIM4 model:

    ********** Common source amp *****************
    M1 out in 0 0 nmos l=60.000n w=1.000u
    V1 1 0 1.200 ac 0
    V2 in 0 250.000m ac 0  distof1 1 0 sin( 250.000m 10.000m 1.000G   )
    R1 1 out 40.000K res_model noisy=1

    .disto lin 4 20meg 50meg

    .model res_model r
    .model nmos nmos level=54 version=4.7


    I tried level 8 also and that one gives me all zeros as well.

    Thank you,

  • Dietmar Warning

    Dietmar Warning - 2012-04-23

    Sorry I was wrong. Small signal distortion analysis is only supported by the ancient spice2 models (bjt, diode, etc.) in ngspice, not for bsim models. Please use the fourier statement and evaluate the output per scripting.

  • Anonymous - 2012-04-23

    Hi Dietmar,

    Thank you for your response. I don't know if it's a bug in NGspice or just incorrect documentation then, because in NGspice-24 documentation, in section "supported analysis" (page 37), all the supported models for small signal distortion analysis are listed:
    diode, BJT, jfet, mosfet(levels 1, 2, 3, 6, 9, BSIM1, BSIM2, BSIM3, BSIM4 and BSIMSOI), and mesfets.

    I guess fourier is another option.
    Thank you so much for your help,


  • Holger Vogt

    Holger Vogt - 2012-04-23

    Nima, Dietmar,

    I will update and correct the manual.



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