R&D Staff Tip of the Month

Publish Date: Jul 18, 2007 | 9 Ratings | 4.22 out of 5 |  PDF


The R&D Staff Tip of the Month allows the software developers and quality assurance staff at National Instruments Electronics Workbench Group to showcase the features of NI Multisim that they know will be helpful to the design engineer.

1. R&D Staff Tip of the Month

A useful and easy-to-use feature in NI Multisim 10.0.1 is the Arbitrary Spice Block component. The SPICE Block is a port-less component that allows you to insert SPICE code directly into a Multisim netlist via a textbox. This means that one does not have to create a new or custom component (or edit a pre-existing device model) to simulate small sets of SPICE code. Once the SPICE Block is placed onto the schematic, you can simply type in the SPICE code to imbed a particular device, configuration or simulation process in any schematic.

 Maksood I

 Simulation and Modeling

 National Instruments Electronics Workbench Group



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2. See for Yourself

In the following example we will place the circuit model of a simple three-terminal opamp into an Arbitrary Spice Block   (figure 1) and set up a simple text-based netlist within the SPICE block. We will then perform transient analysis using the Multisim interface. This example highlights how you can potentially take SPICE code from colleagues, the internet and other sources, and quickly simulate it within the Multisim environment.

Figure 1- Arbitrary SPICE Block component


The opamp and simulation code is contained within the 6370_example_code.cir file attached at the bottom of this article.

  1. To place the block on the workspace select Place>>Component in Multisim
  2. In the Component browser under Group select Basic
  3. Under Family select BASIC_VIRTUAL and you will see the ARBITRARY_SPICE_BLOCK component (as shown in figure 1)
  4. Click the OK button to place the block onto the workspace.
  5. Double-click on the Arbitrary Spice Block and paste the contents of the 6370_example_code.cir file into the text field of the value tab (figure 2) and press OK.

Figure 2 - Entering SPICE simulation data

  1. To simulate the netlist, go to Simulate >> Analyses.
  2. Select Transient Analysis.
  3. Select the Output tab.

In this example we will do a transient analysis upon the V(1) and V(11) nodes.

Figure 3 - Transient Analysis dialog box

  1. Select the node V(1) in the Variables in Circuit section of the Output tab (as seen in figure 3)
  2. Click on the Add button to add the node to the transient analysis.
  3. Repeat steps 9 and 10 above for node V(11).
  4. Click on the Simulate button. You will notice that the grapher will output the waveforms displayed in figure 4.

Figure 4 - Transient Analysis waveform


With these few simple steps we have been able to add SPICE code to our Multisim environment. This SPICE Block can be used to add special commands to any Multisim simulation. For example we can easily create transformers by using the SPICE Block to insert the coupling coefficient between two inductors on a schematic. We can then use Multisim virtual instruments and analyses to understand the overall circuit's behavior.


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