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Reply-To: "Kevin Aylward"
From: "Kevin Aylward"
References: <firstname.lastname@example.org> <8C6F9.email@example.com> <firstname.lastname@example.org>
Subject: Re: SPICE
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X-Inktomi-Trace: public1-pete2-5-cust19.pete.broadband.ntl.com 1038572937 22407 18.104.22.168 (29 Nov 2002 12:28:57 GMT)
Date: Fri, 29 Nov 2002 12:28:53 -0000
NNTP-Posting-Date: Fri, 29 Nov 2002 12:28:58 GMT
Paul Burridge wrote:
> On Wed, 27 Nov 2002 16:42:44 GMT, "Mike" opined
>> I don't know of anything that would prevent SPICE from being an RF
>> simulator, and I use it regularly to simulate circuits in the 2.5GHz
>> range - well into the RF regions. I generally find that my
>> simulation results are not terribly different than the silicon
>> results. What was the problem with the earlier products you tried?
> I'd previously tried EWB/Multisim to model a single RF class C
> amplifying stage . I wouldn't have thought that was *too* demanding,
> but I was getting like 140 - 200v o/p signals as opposed to 2*Vcc as
> it should have been (for a Vcc of 12v) and the waveform o/put was
> highly irregular and not the pure sine wave it should have been.
ASSUME - ASS out of U an ME
You must check models. No one is going to provide 10,000 accurate models
in their library.
> Another niggle was the program didn't seem to register a problem when
> I put 12kv on Vcc! One assumes the full model parameters for the BDX36
> BJT weren't fully included.
Basic Vce breakdown of bipolar is not modelled. This is usually accepted
right of the bat by anyone that simulates regularly. To use spice
effectively, one must do at least some *basic* reading to understand its
limitations, and how to avoid these limitations. You wouldn't use a
scope without looking at its manual, i.e. connecting its input to 12Kv,
so why should a simulation tool be any different?
I wonder how many more device parameters
> weren't included in the other devices in Multisim's libraries.
> A friend of mine in the know told me that EWB is no use for
> RF/non-linear simulations anyway and suggested Symphony or Serenade
> instead. I've yet to try those, though.
The issue here is that for high Q circuits, such as xtal oscillators, it
take a long time to simulate. RF simulators use a different method that
allows steady state time domain response to be obtained in a short time.
Other then this, *if* you have the models, spice will work fine at rf.
There is certainly no basic problem in non-linear analysis in spice,
indeed the other RF simulators cant simulate a non-linear transient at
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.
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