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From: John Larkin
Subject: Re: SPICE simulation goes awry?
Date: Tue, 10 Dec 2002 13:22:20 -0800
Organization: Posted via Supernews, http://www.supernews.com
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On Tue, 10 Dec 2002 15:41:37 +0000, Paul Burridge
>I'm running some tests on a selection of circuits supplied with this
>version of spice I'm currently trying out. I've noticed that when I
>run a TA on a 7Mhz Colpitts oscillator with a 1v supply rail WRT GND
>(this is the specified value in the schematic although it seems
>*bloody* low to me) I get a steadily increasing output signal sine
>wave of well over 13volts (and it's *still* climbing by the time I get
>fed up watching it). How can this possibly be right? It's hardly
>likely in the real world (even with my scope:-)).
A dumb enough transistor model will do this. Clearly the collector
voltage must be swinging far negative, which isn't realistic.
And the 1v rail does look low. Try and see if it oscillates at Vcc=0!
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