Re: [Gnucap-devel] JFET and initial conditions

[al davis]

On Friday 15 June 2007, Xavier Romeuf wrote:
> However, if I add the "uic" option, the initial voltage
> becomes 0, although there is not any specified initial
> condition:
>
> Gnucap> get circuit.ckt
> Gnucap> print tran v(N528849)
> Gnucap> tran 0 1n 0.1n uic
> #Time       v(N528849)
>  0.         0.
>  100.p      0.64275

I get the same results on spice.

> Shouldn't it have given the same results?
> Can the initial voltage of N528849 be defined to another
> value than 0?

The behavior of "uic" is rather strange.  Gnucap does it the 
same way as Spice, except that the "ic" command temporarily 
doesn't work.  The "ic" options of the components should work, 
giving you a way to have a non-zero initial condition.

"uic" just jams in the numbers, using 0 for anything that is not 
specified.  No solution is done.  There are no checks for 
validity.  This is identical to the way Spice does it, 
intentionally.

The "ic" command is broken, and will be fixed eventually, 
probably by the next official release, but not for the next 
development snapshot.