Re: [Help-gnucap] diode models

[al davis]

On Fri, 22 Jul 2016 17:07:51 -0500
John Griessen <address@hidden> wrote:
> and gnucap says, "non-recoverable convergence failure, reducing (itl4)
> newtime=3.300000e-05  rejectedtime=3.300000e-05
> oldtime=3.300000e-05  using=3.300000e-05 tried everything, still
> doesn't work, giving up"

What version of gnucap are you using?

In older versions, there used to be a bug that sometimes messed up time
stepping, causing duplicate time steps, rejecting a step that was
actually good and repeating exactly the same time. It had something to
do with floating point truncation.  I thought it was fixed a few years
ago.

If it's a recent version, I want to see your circuit.


On Fri, 22 Jul 2016 17:07:51 -0500
John Griessen <address@hidden> wrote:
> .model 1N4007 D(IS=7.02767n RS=0.0341512 N=1.80803 EG=1.05743 XTI=5
> BV=1000 IBV=5e-08 CJO=1e-11 VJ=0.7 M=0.5 FC=0.5 TT=1e-07 mfg=OnSemi
> type=silicon)

Some of the parameters here are proprietary extensions in some versions
of Spice.

As you figured out ..  Forward voltage drop of a diode is determined
mainly by the parameters IS, N, and RS.  If you are fitting it
expermentally, and have two data points, choose IS to match the
forward voltage at a low current (where the diode exponential is more
pure), then RS to match at a high current (where ohmic resistance
dominates).


As Felix said, the "native" diode model doesn't implement breakdown.
There are several alternatives available as plugins in
git://git.sv.gnu.org/gnucap/gnucap-models.git
These models are what they are, which may be better or worse than the
"native" "modelgen" model.