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Monte-Carlo-Simulation

  The Monte-Carlo-Simulation also is a paramteric simulation.

  To start the Monte Carlo Simulation, there must be a Monte Carlo Simulation Box inside the schematic. (See picture 12.3)


  
Figure 12.3: Properties of the Monte Carlo simulation box
\fbox{
\includegraphics{monte_carlo.ps}
}

 

To perform such a simulation, you have two possibilities. First, you can edit the 'model' -property of passive components like resistors, capacitors and so on or the model-property of bipolar and MOS transistors. The model property consists of two parts: the kind of statistical distribution (flat or gauss) and the standard deviation.   Both values have to be separated with a '/' or a '#', i.e.
'flat/0.1'.
'flat/0.1' means that the standard deviation   is 10% of the nominal value of the property.
'flat#0.1'
means that the standard deviation of the property is 0.1.

Setting the model-property to '(none)' means that the device property value remains constant during simulation. It is okay to use expressions specifying the standard deviation, i.e.
'gauss/stdevcap'.

  The second possibility to specify parameters with distribution is to fill out the entries in the Monte Carlo Simulation Box. The model and standard deviation for all parameters are identical if not set explicitly.

Please check that you don't use the same parameter in the simulation box and as a property parameter inside a device with a specified monte carlo model. There would be unpredictable interference between these two parameters.

  Starting the simulation is done inside the 'parametric*'-menu selecting the run monte carlo-Button.

  Selecting select V(x) lets you choose a single node you can plot after simulation . Selecting select I(x) lets you choose a single terminal.

If you want to plot multiple nets or terminals, please use the waveform calculator (see page [*]).

Circuit optimization is the third parametric siulation type and will be treated in a subsequent chapter.

Up to SPICECAD version 1.2, a Monte Carlo Simulation could be performed only on device parameters like gate lengths and widths and component values like resistances, capacitances etc.


next up previous contents
Next: Using the pre-processor cpp, Up: Simulation Previous: Parameters
Martin Maschmann
1999-10-10