Ski,

  Are you referring to Virtuoso IC614? Spectre is a simulator. The
basic recommendation would be to up version to the most recent
IC615 ISR release. There have been a significant enhancements
in to statistical analysis tools, in particular, support for confidence
intervals and Monte Carlo auto-stop are new for IC615. I think that
the issue of the appropriate number of samples to select is complex
question, which is why using some of the new tools, such as, Monte
Carlo auto-stop, might be useful. Another option is to use one of
the alternative sampling methods, for example, orthogonal sampling.
Using orthogonal sampling should give better estimates with fewer
points. Also since you are simulating a sense amp, you might want
to consider using High Sigma Yield estimation since you probably
are looking for more than 3 sigma yield.

                                                         Best Regards,

                                                             Sheldon