Consider the following active filter circuit.
This circuit can be found in EXAMPLES/MonteCarlo/cheb.sxsch
The circuit is a 5th order low-pass 7kHz Chebyshev filter with a 1dB passband ripple specification. Its nominal response is:
This circuit is to be used in an application that requires the gain of the amplifier to remain within 2dB of the dc value from 0 to 6kHz. A 1dB ripple specification therefore seems a reasonable choice. Clearly though the tolerance of the capacitors and resistors may upset this. To investigate, a Monte Carlo analysis is required. The standard part tolerances are 10% for capacitors and 1% for resistors. With the example circuit the tolerances are already applied but the procedure for doing this is as follows:
Start the analysis in the usual way. It takes about 2.5 seconds with a 1.5G P4.
The analysis will be repeated 10 times. Now plot the output of the filter in the usual way (). The result is the following:
As can be seen, the specification is not met for some runs.
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