[SI-LIST] Re: [Negative Circuit elements?]
- From: "Loyer, Jeff" <jeff.loyer@xxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Tue, 5 Aug 2003 07:18:09 -0700
Eric Bogatin did a nice job of explaining the negative values. It's in =
the archives -=20
"non-negative off diagonal capacitive matrix elements", Sun, 2 Sep 2001.
Jeff Loyer
-----Original Message-----
From: Steve Corey [mailto:steven.corey@xxxxxxxxxxxxxx]
Sent: Monday, August 04, 2003 7:46 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: [Negative Circuit elements?]
Se-Ho -- be careful with negative element values, since they can cause a =
lot of problems. As you have stated, they can make your model=20
non-passive, and if so, it will blow up under some circumstances.
If you have complete control over how your model will be used (frequency =
range and terminations), and you can show that it's stable (which is=20
weaker than passive) over that subset of terminations and frequency=20
range, then you're OK. Or, if you can prove that your model is passive=20
despite the negative elements, you're fine there as well.
As to why SPICEs accept negative elements -- simulators are differential =
equations solvers, but not passivity checkers. Those elements=20
correspond to a valid set of differential equations, but not necessarily =
a passive system.
-- Steve
-------------------------------------------
Steven D. Corey, Ph.D.
Time Domain Analysis Systems, Inc.
"The Interconnect Analysis Company."
http://www.tdasystems.com
email: steven.corey@xxxxxxxxxxxxxx
phone: (503) 246-2272
fax: (503) 246-2282
-------------------------------------------
You Se Ho wrote:
> To Dear all:
>=20
> Is it Ok to use negative RLCG values in Spice simulation for time
> domain and frequency domain simulation if I happen to have those =
negative
> circuit element values? Passivity is one possible reason that people =
say
> no that I can think of. I cannot find definite answer not using =
negative
> values. Anyway Pspice allows me to use those values, I think there is =
a
> reason for it.
>=20
> Thanks
> sincerely,
> se-ho You
>=20
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