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 - Winter 2006


Question: I recently purchased a new computer. I copied the entire Micro-Cap directory over from the older system and then reinstalled the security key driver. The program loads fine, but when I attempt to simulate one of my existing circuits, I get the error message:

No such file or directory D:\MC8\DATA\MyCircuit.TNO

Isn't the TNO file the numeric output file? Why does it need to find it at the beginning of the simulation and how do I resolve this error?

Answer: The TNO file is the numeric output file for transient analysis. At the beginning of the transient simulation, Micro-Cap will create the TNO file to begin writing data to. In this case, the file is not the problem, it is the directory path that Micro-Cap is objecting to when trying to create the file. Most likely, when Micro-Cap was copied from one system to the other, either the partition or the directory that it was located in changed between the source and destination systems. Since the entire Micro-Cap directory was copied over, the new system is using the path references set up for the old system. To remedy this, go to the File menu and select the Paths option. Make sure that the paths specified for the Data field actually exist on the new system. Once this path has been corrected, the error message should no longer appear.

Question: I am trying to determine the continuous effective power at my load resistor. I plot the following expression:


but this doesn't produce the results I am looking for. When I plot the next expression:


I get the expected curve. Why is there a difference between the two?

Answer: The difference occurs due to the point at which the RMS operator takes effect. In the first expression, the RMS is being calculated based on the instantaneous power of the resistor which would be equivalent to:


In the second expression, both the current and voltage have their RMS value calculated individually, and then the two RMS values are multiplied together. The second expression is the commonly accepted definition for determining power in AC circuits.

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