Monte Carlo Analysis

 

Like parameter sweeps, Monte Carlo analysis can be run in conjunction with any tests. Just select the test you wish to perform from the Test tab, set up the test parameters as described in the individual tests, and click on the Monte Carlo tab to set up a Monte Carlo analysis.

To set up a Monte Carlo analysis, click on the Monte Carlo Setup button. This will bring up the following dialog box:

The number of runs (or number of times to randomly vary the chosen parameter) is set in the # Iterations box. For each run, a set of device parameters is assigned randomly according to the parameter's range and distribution type. To select and set up the device parameters for variance, select the appropriate parameter from the available tabs. Resistors and capacitors distributions are set through their own buttons because Monte Carlo tolerance is built into the model and require its own setup. For other devices, use the Edit Distribution button to set up a particular parameter for Monte Carlo analysis. Clicking any one of these buttons will bring up the following dialog box:

 

 


The name of the Part/Parameter that you are setting the distribution for is displayed in the Parameter box. Use the Random Type drop down box to set the Distribution Type. If you specify Tolerance as a percentage, then it will be interpreted as a percentage boundary on either side of the individual parameter's given value. The main types of distributions are Gaussian and Uniform. Gaussian distribution is the bell shaped distribution, and Uniform gives any value in the range an equal probability. To set individual parameter monte-carlo distributions, edit the model properties of any part in the circuit and if the model parameters are available, then you should see an area where you can edit the range and distribution type for the parameter.

Results of the Monte Carlo Test can be displayed in a 2D graph, 3D graph, or a Histogram, which displays the distribution frequency of the results. Each graph type is set up under the respective tab in the Monte Carlo setup area. When specifying the Histogram, the results will appear as a set of curves.

When running a monte-carlo simulation, at each simulation iteration, parameters are set to values that are different than their specified values according to their tolerances.
When you have more than one parameter being offset by a tolerance, sometimes you may want them to move together, and sometimes you may want them to move distinctly.