orcad pspice User Manual

Chapter 12    Monte Carlo and sensitivity/worst-case analyses

runs, saving the DC analysis output from those five 
runs.

PSpice starts by running all of the analyses enabled in the 
Simulation Settings dialog box with all parameters set to 
their nominal values. 

However, with Monte Carlo enabled, PSpice saves the DC 
sweep analysis results for later reference and comparison. 
After the nominal analyses are finished, PSpice performs 
the additional specified analysis runs (in this example, DC 
sweep). 

Subsequent runs use the same analysis specification as the 
nominal run with one major exception: instead of using 
the nominal parameter values, the tolerances are applied 
to set new parameter values and thus, new part values.

There is a trade-off in choosing the number of Monte 
Carlo runs. More runs provide better statistics, but they 
require more time. The amount of time scales directly with 
the number of runs: 20 transient analyses take 20 times as 
long as one transient analysis. During Monte Carlo runs, 
the PSpice status display includes the current run number 
and the total number of runs left.

Figure  75

Monte Carlo analysis setup for EXAMPLE.DSN.

PSpice offers a facility to generate 
histograms of data derived from Monte 
Carlo waveform families through the 
performance analysis feature.

For information about performance 
analysis, see 

.

For information about histograms, see 

.

Pspug.book  Page 290  Wednesday, November 11, 1998  1:14 PM