Simulating circuits using the spice in national instruments multisim

Simulation overview

While a good design naturally follows from quality schematics, truly great designs can made with the help ofsimulation. Multisim provides powerful simulation capabilities and features which are simply unavailable in other EDA packages.

Simulating a design can result in fewer design iterations and less chance of errors in the prototype stage ofproduct development. When a design is simulated at the front end of the design process, the number of design cycles can besignificantly reduced.

In addition to a world-class SPICE simulator, Multisim also includes XSPICE simulation, enabling fast simulationof digital other components.

Patented co-simulation techniques allow designers to simulate VHDL modeled components along with the restof a circuit. With MultiMCU, certain microcontrollers can be simulated in the very same mixed-mode environment. MultiMCU is notavailable for all versions of Multisim.

Using the interactive simulator

To begin a simulation, ensure that the circuit has all the necessary prerequisites. All circuits must include aground reference, and a source. Once the circuit is ready for simulation, click the Run / Stop Simulation button

The settings that are used for interactive simulation can be viewed and modified by selectingSimulate/Interactive Simulation Settings.Figure 1 below illustrates some of the settings available for interactive simulation. Thedefault end time for the simulation is 1e+30 seconds, or around 3.17e+30 billion years. By default time steps will be generatedautomatically.

To view results of this simulation, the measurement probe

• Voltage (instantaneous, peak-to-peak, RMS, and DC).
• Frequency.

Virtual instruments can also display simulation results. Virtual instruments are covered later in thissection.

Multisim also provides more traditional SPICE analyses, which are run through the Grapher/Analyses List toolbarbutton,

Handling simulation errors

Sooner or later, even the most experienced SPICE users will run into a SPICE simulation error. Multisimincludes a simulation advisor to help discover and fix the source of troubling errors.

When an error message appears such as the one in Figure 5, click the Adviser button to access the availablehelp.

Two of the most often encountered errors are timestep errors, and singular matrix errors. below provides themost common solutions to these simulation errors.