Re: [Qucs-help] Simulation error in Qucs at an astable multivibrator

[Stefan J. <st...@gr...>]

Am Mi, 31.05.2006, 15:09, schrieb Markus Weissbacher:

Hello Markus,

> I dont want to annoy you, I just haven't fount that error neither in the
> faq nor in the mailing list, it might be, that I have just done someting
> wrong in the program.

  you don't annoy me at all.  Thanks for the report.

> This is an astable multivibrator, the problem is, that when I change R2
> from 1k to 100Ohm the simulation runs, but has several warnings, which I
> dont understand. If R2 stays 1k it doesn't even simulates.
>
> I have also discovered a similar error in pspice, it doesn't work eighter.
> I have built this network in reality and there it does a rectangle signal
> with about 3.3kHz.

I think you expect a 3.3Hz (not 3.3kHz) don't you?  Otherwise I don't
understand why you wait for 1000ms...

Bistable circuits are always a problem in transient simulation.  First
you should replace the ideal diodes/transistor with real models of the
devices you in fact used.  Probably you find a SPICE model for these?  Or
do you know all the parameters of them?  Then you can fill these values
into the properties of the models in Qucs.

I played around with your circuit and put in some models from the
library manager.  Then I was able to get a 3.3Hz signal...

Cheers, Stefan.