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From: "Mike Engelhardt"
Subject: Re: PSpice and temperature
Date: 29 Dec 2002 02:50:07 GMT
Organization: Concentric Internet Services
X-Newsreader: Microsoft Outlook Express 5.50.4807.1700
>>> Does anyone know, can SPICE (specifically, PSpice) model the effects
>>> of temperature on a device-by-device basis? How do I tell it to do
>>> that? I'm trying to get a better understanding of what happens in a
>>> small class-AB audio amp when there's a thermal mismatch between my
>>> output transistors and my bias-setting devices.
>>Yes, you can override a transistor's instance temperature.
>Forgive my unquestioned ignorance of computer modeling, but I don't
>see how one can rely on the figures posted in order to accurately
>determine the heat transferences involved. There are (IMHAIIO) too
>many variables involved that would be far more speedily and accurately
>accounted for by simply modifying the physical circuit for optimum
>results. I mean (for just one example) how can you assume you know the
>specific heat capacity of the thermal transfer compound the OP is
SPICE doesn't solve for the temperature of the circuit. It
computes under the assumption that each component is perfectly
connected to an infinite heatsink at the user-specified circuit's
temperature. This is useful as a first go for a low-power IC all
one one substrate, but can be problematic assumption for board-
level power circuits. I understood the original poster's
question was how to override this temperature on an instance-
by-instance basis for transistor elements in a simulation in the
interest of investgating the thermal effects. The very question
implied an understanding/awareness of the behavior of the
Hope this helps,
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