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"the following branches form a loop of rigid branches"

Jose Sarmento

Hello all,

I'm designing an xpair for a sinusoidal oscillator, and while doing an ac analysis, the following error appears:

The circuit is as follows:

From the error, it is plain that the AC source V1 is causing the trouble, but I can't understand why exactly.

Thank you

Parents

  • The reason is that during DC the inductors are shorted, so that means that the voltage source V1 is shorted - which means you would have an ill-conditioned matrix. Even though the voltage source might be 0V at DC, the equations would still have this problem.

    Since your inductors are (presumably) ideal analogLib inductors, I would suggest setting the resistance parameter of one or other of them (or both) to a small value (e.g. 1mOhm; in general you should not use smaller resistor values than 1mOhm as this can lead to convergence difficulties). That will prevent the problem.

    Andrew

  • in reply to Andrew Beckett

    Interesting, did not think that through. Your suggestion fixed it, thank you so much!

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