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From: jws@mintaka.mlb.semi.harris.com (James W. Swonger)
Newsgroups: sci.electronics
Subject: Re: Filter simulation in Pspice
Message-ID: <1990Nov9.190825.21614@mlb.semi.harris.com>
Date: 9 Nov 90 19:08:25 GMT
References: <1990Nov9.160343.3301@sunee.waterloo.edu>
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 The Large Resistor To Ground trick is one of the most straightforward ways
of improving convergence. You may be able to explicitly set initial conditions
on your PSpice element cards (current for inductors, voltage for caps). If you
know the initial conditions this should help quite a bit. Also see whether 
PSpice has a store/restore capability with which you can save the DC solution
and use it to initialize the circuit state for the next. Finally, see what 
you have available to you as far as setting the number of DC iterations, 
required tolerances for "convergence", etc. You may just need more iterations.
Note also that a filter with only AC components is going to be hard to
solve for a computer - any error is going to make everything "sing". Try 
putting large resistors in parallel with the caps and very small resistors in
series with the inductors (small being a judgment call based on frequency of
interest). This may provide a means for the errors to damp out.