Home Forums Bug Reports Transient simulation of a bipolar transistor fails

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  • #893
    azozaya
    Participant

    Hi:

    I have created a schematic model for the BFP640 Infineon transistor by my own editing the SPICE file (.cir) obtained from the Infineon website and importing it to QucsStudio. Although the s-parameters simulation is performed quite well, the transient simulation for an input sine wave at 1 GHz during 20 ns does fail (see the attached snapshot). In order to check my model, I have used the same SPICE model in LTSpice and I have obtained the correct results (see the attached snapshot). Perhaps I doing something wrong in QucsStudio.

    Thanks

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    #896
    zhu
    Participant

    The configuration settings are not shown: the integration method must have been very likely the default “Trapezoidal”. Experiment with the Gear methods from Properties\Gear1 upwards.

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    #898
    azozaya
    Participant

    Thanks Zhu for your answer, but I have already proved all the integration methods without succeed

    #905
    QucsStudio
    Keymaster

    Can you share the schematic files? Otherwise it’s not possible to investigate the problem.

    #915
    azozaya
    Participant

    Attached you will find the schematics

    #916
    azozaya
    Participant

    Attached you will find the schematics (I hope)

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    #918
    QucsStudio
    Keymaster

    There’s indeed a bug in the substrate capacitance that causes this problem. If you set Cjs of the BJT to zero, it should work. You can add the Cjs value to Cj of the diode in order to reach the same value again.

    Thanks for reporting the problem! It will be fixed in the next release.

    #919
    azozaya
    Participant

    Thank you very much

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