Transient simulation of a bipolar transistor fails

[azozaya]

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

Attachments:

1. 

   QStudio.jpg
   

2. 

   LTSpice.jpg
   

[zhu]

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.

Attachments:

1. 

   TR.png
   

[azozaya]

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

[QucsStudio]

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

[azozaya]

Attached you will find the schematics

[azozaya]

Attached you will find the schematics (I hope)

Attachments:

1. BFP640_e.zip

[QucsStudio]

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.

[azozaya]

Thank you very much

[Author]

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