Hot and Cold Running SPICE

[sbench]

Another tip. Spice allows you to model temperature effects if you care to. There is a built in parameter called TEMP which you can set and manipulate. The resistors (and most other components too - but that feature is "undocumented") support an extension to their value field called TC. The first parameter you enter is the first order (linear) temperature effect. You can follow this with a comma and another value which will be the second order (square) effect etc. THIS ALLOWS YOU TO MODEL THE EFFECTS OF COPPER WIRE (or silver etc) in inductors and transformers, (and Dave's copper wire wound resistors). For instance, a 1k ohm copper wire can be modeled by entering "1k tc=.00404" in the value field, since copper has a temperature coefficient of .00404 per degree c.

You can then set the temperature to what you like and see the effects on your circuit. You can step the temperature through the "normal" "Step" command. If you select the DC operating point as the simulation type, and step the temperature, Spice will plot your selected nodes as a function of temperature. The attached file is a simple example of how this works.

Steve