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: I have a SPICE text file from another program that I want to analyze in Micro-Cap. The name of the file is RINGDIF.CIR. Whenever I try to load this in Micro-Cap, I get an error stating that I "Must run CONVERT for 'RINGDIF.CIR' to force a conversion." Is it possible to analyze a SPICE text file?

Answer: Both SPICE and PSpice text files can be run directly in Micro-Cap. The problem in this case is the extension of the file RINGDIF.CIR. Micro-Cap assumes that any file with the extension .CIR is a schematic file, and since it doesn't recognize the SPICE file as a compatible schematic format, it returns the convert error. The procedure for fixing this is simple. Just change the extension of the file to .CKT. The file RINGDIF.CKT would be able to load and run without a problem.

Question: I have created a circuit that contains an opamp. The opamp is only being used for its gain capability so I have no need for all of the other modelling capabilities of it such as slew rate limiting, saturation, offset, etc. How can I change the opamp model so it is an ideal opamp?

Answer: Double click on the opamp while in select mode to invoke its Attribute dialog box. In this dialog box, highlight the MODEL= attribute by clicking on that line in the list window. When this attribute is highlighted, the Edit command button in the bottom right of the dialog box should be enabled. Click on the Edit button. This extends the dialog box in order to display the parameters of the model statement. Changing the Level parameter to a value of 1 will model an ideal opamp. The only parameters that are used with the Level 1 opamp are the A, ROUTAC, and ROUTDC. This model level is represented by a current source and a resistor.

Question: I am running a Probe Transient Analysis on my circuit. When the analysis is finished, the schematic portion of the split screen has some of its wires missing. I can click on where the wire should be and a waveform will appear, and when I exit analysis and go back to the schematic, the wires are fine again. What is happening?

Answer: The wires that are disappearing should be connected to a node that is purely digital. (Purely digital nodes can be known from the fact that when the node numbers are displayed, the node number is within a rectangle. For analog and mixed nodes, the node number is within an oval.) In a Probe analysis or when in Animation mode for an analysis, the wires connected to digital nodes will change color to represent the last digital state that has been calculated at that node. In the case described, the color of the wire for the state calculated happens to match the background color of the window making it appear as if the wire disappeared.

To view the defined colors of the digital states, invoke the Properties dialog box for the schematic. This dialog box can be invoked by hitting the F10 hotkey, double clicking in the schematic while in select mode, or by clicking on the Properties icon. Go to the Color/Font page of the dialog box. At the bottom of the Objects list are the digital state entries. Highlight an entry to view or edit its color.
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