Monte Carlo Simulations
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Transcript Monte Carlo Simulations
Experiments 8 and 9
Monte Carlo Simulation
Monte Carlo simulations in PSpice can be run as either:
a worst case analysis where the maximum deviation from
the nominal values of each component are used in the
calculations
a statistically-driven variation from the nominal values of
the components using a bell shaped curve for the
distribution of deviations.
Prior to Monte Carlo
• Set up a Simulation Run using Analysis Setup
– You must select one of the other types of analysis first
–
Click on DC Sweep
–
Pick either of the voltage sources to sweep
• Make both the start and end
values equal to the nominal
value of the voltage source
• Pick any value for the
increment.
• Click OK.
Analysis Setup
Select Monte Carlo/Worst Case
In the pop-up window, enter the number of runs in MC Run
At least 500 is recommended for statically reasons
Not more than 2000 due to run time issues
Do not unselect the Bias Point Detail
Monte Carlo or Worst Case
• In Output Var: box, enter V(node
name) or V(component:node)
• This is the advantage of labeling
the nodes. So, you will enter V(X)
and V(Y) for the two Monte Carlo
simulations that are required.
–
Note that you will also have to put a
voltage marker on to the circuit
schematic no matter what you put as
the output variable
– If you have selected a DC Sweep,
select DC as the Analysis Type.
Monte Carlo or Worst Case
Select All on the MC Options.
Then, click OK.
Once the schematic is saved,
you are ready to run the
simulation.
Open the Plot Window
Click OK.
Output Plot is a Histogram
Histogram
The shape of the histogram and the values of the mean,
maximum, and minimum voltages at node X will differ
every time you run the simulation because a random
number generator is used to determine the values of
each of the five resistors in every one of the runs.
The differences in the mean, maximum, and minimum
values are negligible if sufficient number of runs are
entered in the MC Run box when you set up the simulation.
The shape of the histogram becomes more symmetrical as
the number of runs approaches 2000.
Your Experimental Results
If your voltage supplies are exactly +5 V and +9 V, then
the voltages that you measure at nodes X and Y should
fall somewhere within the range from the minimum to
maximum values of the voltages calculated during the
Monte Carlo simulation.
If you measure the actual values of the +5 V and +9 V
supplies and enter them into the simulation, then there is a
100% likelihood that your measurements will fall within this
range.