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


Question: When I run my circuit it says it can't find a particular subckt part. What did I do wrong?

Answer: Micro-Cap 6 expects to find all subckt and model statements in the default data directory or in the location specified by the environmental variable MC6DATA. Usually this problem occurs because you have recently changed the data directory or the MC6DATA variable and MC6 can't find the library containing the subckt. Remember, when you use the file dialog box to open a file in a new directory, you change the default directory to the one just opened.

Let's say you have a circuit called A.CIR that uses a small library file called ABC.LIB. Let's assume that both are happily living in a directory called c:\mc6\project2 and that you routinely work from this location. Now you start a new project and you create a new folder at c:\mc6\project3 and copy the circuit file A.CIR into the folder to use a starting point for the new project. You change the A.CIR a little and try to run a transient analysis. You get the message "No such file or directory c:\mc6\project3\ABC.LIB". That's because the current data path is c:\mc6\project3 and there is no ABC.LIB file there.

There are two general solutions to this problem:

1) Keep both model library files and circuit files in the same location.

2) Keep the libraries in a path specified by the environmental variable MC6DATA. Then you can use one or more circuit directories to work out of. To modify the MC6DATA value in W98, you must add this line to your autoexec.bat file on the boot drive (usually the C drive).


where C:\MC6\MYLIBS is the path to your model directory.

NT has its own way of setting the environmental variables. Go to the Control Panels and double click on System. Go to the Environment tab. There are two text fields: Variable and Value. Variable would be MC6DATA and Value would be the path to the desired directory. After typing these in click the Set command button, click OK. It should work after this.

Question: There are two ways to draw an orthogonal wire between two points. How do I change the way the program has chosen to draw the wires as I'm drawing them?

Answer: Click the right mouse button while dragging the wire. This will toggle the two-branch wire between the two possible routes.

Question: What is Gear integration and when should I use it?

Answer: Infrequently and with caution. There are two type of integration methods available, Gear and trapezoidal. Trapezoidal is the default method and is the best choice for most circuits. However, for power circuits where inductors are being switched by diodes or other devices, Gear is sometimes the best choice. It is a lossy integration method which attenuates high frequency oscillations that, while technically correct, are of no interest to the user and tend to slow down the simulation. The one area where you should definitely avoid Gear is in LC oscillators. A pure LC tank circuit with an initial voltage on the cap will oscillate forever with trapezoidal integration, but will rapidly decay with Gear integration.
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