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Importing a MOSFET model into Multisim

Primary Software: Electronics Workbench>>Multisim
Primary Software Version: 10.0.267
Primary Software Fixed Version: N/A
Secondary Software: N/A

Problem: How do I import a SPICE MOSFET model that starts with a “.MODEL” statement into a Multisim component?

Solution: Any SPICE model that starts with “.model” is a core model, and the Multisim SPICE engine already has the pin template defined. The Multisim SPICE engine expects the MOSFET model to have four pins. If you used a three pin symbol, Multisim will simulate with an error message. For example, the model you want to import into a component is similar to this:

.MODEL B4 NMOS VTO=1.7 KP=322E-6 LAMBDA=0.005
+CGSO=2.5E-9 CGDO=2.5E-9

The general form for a SPICE MOSFET is:

Mxxxx D G S B model_name

To use the above model in a three pin symbol, you must use a “.SUBCKT” statement and tie the “S” and “B” pin together internally. Here is an equivalent model:

.SUBCKT MOS D G S
M1 D G S S B4
.MODEL B4 NMOS VTO=1.7 KP=322E-6 LAMBDA=0.005
+CGSO=2.5E-9 CGDO=2.5E-9
.ENDS

Note the two “S” nodes on the “M1” line. This is how you connect the “S” and the “B” pin together.

If you do not want to modify the model, you must use a four pin symbol.

Related Links: http://zone.ni.com/devzone/cda/tut/p/id/3173 http://zone.ni.com/devzone/cda/tut/p/id/5413

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Report Date: 06/07/2007
Last Updated: 06/12/2007
Document ID: 4A6ANQMC

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