Home Forums Usage Transient analysis convergence issues

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  • #857

    In experimenting with the Qucs ideal library I found the Diff and Int functions didn’t work so I reconstructed schematics to debug them. The schematics didn’t work in Qucs or QucsStudio but do work in Qucs-S and LTSpice.

    I realize theĀ  functions are not realistic and the data they produce is suspect but I was wondering why I couldn’t get QucsStudio to work regardless of the integration method I chose.

    Attached is the Diff schematic



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    If a voltage step is applied to a capacitor, this results in an infinite high current. Especially, the trapezoidal integration method encounter problems here.

    Anyway, it would be a good idea to catch such events in order to work around it. This is on the todo list for coming QucsStudio versions.


    I only mention the issue because I put the identical circuit into Qucs-S, 5Spice and LTSpice and they ran the circuit. I realize the circuit is not a realistic one but I also tried the usual trick’s of adding series/parallel resistors and still couldn’t get it to run.

    I do wonder why Qucs has 4 components in the Ideal Library that don’t work.

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