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From: John Devereux
Subject: Re: SPICE model of XTAL
Date: Tue, 10 Dec 2002 10:11:07 +0000
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firstname.lastname@example.org (Allan Herriman)
>On Mon, 09 Dec 2002 21:05:45 +0000, John Devereux
>>In addition to the other answers, I would like to say that I
>>found it surprisingly difficult to simulate xtal oscillators
>>in spice (after I had made a model). The problem is the very
>>high Q of crystals. You may need to allow many thousands of
>>cycles of circuit operation (in transient analysis mode) to
>>build up a detectable oscillation.
>Is there any reason that you can't set the initial voltage (or
>current) on one of the C or L elements to inject the right amount of
>energy into the tank so that it starts oscillating at full amplitude
>right after "turn on"?
This is what I ended up trying. However, it still doesn't
help much because an unloaded xtal will then happily
"oscillate" for a few hundred thousand cycles whether the
rest of the circuit is connected or not! You still have to
simulate thousands of cycles before you can see whether or
not the amplitude is decaying.
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