[SI-LIST] Re: Spice
- From: Alan Hilton-Nickel <alan@xxxxxxxxxxxxxxxxx>
- To: ivor@xxxxxxxxxxx
- Date: Thu, 03 Feb 2005 10:15:02 -0800
Ivor,
I could be wrong, but I don't know of a better place to ask SPICE
questions. As for newbie questions, you've gone about it the right way
by indicating you've invested some effort before asking a pretty
specific question. It sounds like your simulation model is correct, at
least on paper, but I don't know what you mean when you say the waveform
isn't what you expected. You should be getting a "step" waveform, with
the voltage rising initially to the Vin/2 level and staying there (since
you're perfectly terminated). If you vary the termination at the far end
you should see some reflections. What waveform did you get? And where in
the circuit are you probing?
Alan
Ivor Bowden wrote:
>Hi SI Experts,
>
>I have finally decided to get to know Spice, after many years of circuit
>design work, mostly digital. To this end I downloaded the SIMetrix Intro
>v5.0f program, and also acquired a copy of PSPICE 9.1 Student Version. I
>have only worked with SIMetrix so far.
>
>I realize this is probably not the place to ask newbie questions about
>basic SPICE operations, so my first question is, can anyone suggest any
>good resources (url, list server, news group, etc) to find useful
>information and / or ask these types of questions? Web search finds
>overwhelming hits to pick through, specific recommendations are appreciated.
>
>That being asked, my next question is what is the appropriate way to
>model a coax cable or a PCB trace, driven by a pulse? I set up a pulse
>voltage source (which I assume to be "perfect", that is no source
>impedance), a 50 ohm series resistance to represent the source
>impedance, a 50 transmission line grounded on both sides of one
>conductor, and a 50 ohm resistor to ground at the end. But the resulting
>waveform was not exactly what I expected..
>
>Thanks for any comments,
>
>Ivor
>
>
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