Spectrum Software
Industrial Strength Simulation




Spectrum Software has released Micro-Cap 11, the eleventh generation of our SPICE circuit simulator.

For users of previous Micro-Cap versions, check out the new features available in the latest version. For those of you who are new to Micro-Cap, take our features tour to see what Micro-Cap has to offer.




Questions and Answers - Spring 2008


Question: I would like to sweep a resistor in DC analysis so that I can plot the resistance along the X-axis versus my voltage and current plots. How do I do this?

Answer: For a DC analysis sweep you need the MODEL attribute for a resistor defined. Do the following:

1) For the resistor that you want to sweep, double click on that resistor and define the MODEL attribute. For this example, we will use the name RMod. Make sure that the model name is unique to this resistor in the schematic. Set the RESISTANCE attribute value to 1 (I'll explain why in the following step).

2) Go to DC analysis. For Variable 1, choose the appropriate resistor model in the Name attribute from the drop down list. You should see an entry such as RES RMod in the list if the model name was RMod. Set the second field so it specifies the R parameter. In the Range field, enter the range that you would like the resistance swept through. The R parameter is a multiplier and multiplies the Resistance value. That is why we set the Resistance attribute to 1 previously so that we can sweep R with the actual resistance values directly in the Range field.

Question: I need to create a resistor that varies with the voltage of a node in my circuit. How do I model this?

Answer: Simply enter the expression that you want to use into the RESISTANCE attribute of the resistor. For example, if you wanted the resistor to reference the voltage at node Mod, you would use V(Mod) in the expression. You can combine this with other operators or circuit variables to create any number of equations.

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