Re: [Help-gnucap] gnucap error

[al davis]

On Thursday 07 July 2011, Ramiro Aceves wrote:
> Now the error about the diodes disappeard. I can enter gnucap
> and have the warnings:

> Rc2.X1: Rideal: effective length is negative or zero
> Re1.X1: Rideal: effective length is negative or zero
> Re2.X1: Rideal: effective length is negative or zero

> When I simulate the circuit I get:
> 
> gnucap> tran
> 
> #Time
> open circuit: internal node 54
> did not converge
>   0.
> very backward time step
> convergence failure, reducing (itl4)
> newtime=9.155273e-13  rejectedtime=1.831055e-12 
> oldtime=0.000000e+00 using=1.000000e-12
> tried everything, still doesn't work, giving up
> gnucap>

The warnings are the key to fixing the problem.

Apparently, the resistors are not what you think they are.

I did a quick check on what is happening here ...  That model is 
implemented to an ancient Hspice spec .. where it's all 
specified as length and width.  So, really, the resistors are 
not what you think they are.

Looking at your netlist .. you don't need the ".model" 
statements Rideal or Rnoise .  Just leave them out, and also 
leave out the reference to them.


There is also an issue with the zener diode.  The native model 
doesn't do breakdown.  With the development version, use a 
plugin for the diode model ..  from the spice models tarball.