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.




Transient Analysis


When I view the current through a resistor in either Probe analysis or by using the expression I(R1) in my analysis limits, the polarity of the current is reversed from what I expect. Why is it giving me these results?


In SPICE, the resistor, inductor, and capacitor all have polarity. SPICE uses this polarity in order to determine the polarity of the current and voltage that is present through the part. If your waveform is reversed, it probably means that the resistor needs to be rotated so that the leads are swapped. To view which side is positive and which is negative, double click on the part while in Select mode. In the Attribute dialog box, enable the Display Pin Names check box and hit OK. The pin names for the resistor will now be displayed on the schematic. Current is defined as positive when moving from the positive pin to the negative pin.

You may also change the shape of the resistor and capacitor so that they display a + and - just as the inductor does. There are shapes already created for this purpose. In the Attribute Dialog Box, select the SHAPEGROUP attribute. In the Value field at the top, click on the drop down arrow. A list of available Shape Groups for the part will appear. Select Polarity. Hit OK, and the shape for that specific component will now be changed to show the + and - signs.






AC Analysis
Analysis - General
DC Analysis
Dynamic DC
Initial Conditions
Monte Carlo
Schematic Editor
Transient Analysis