User Guide

Terms You Need to Understand 1
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Each aspect of a design’s performance is found by either:
• first performing the appropriate simulation, then running
Probe to measure characteristics of the resulting
waveform(s), or
• evaluating PSpice Optimizer expressions.
In many cases (particularly if there are multiple conflicting
specifications), it is possible that the PSpice Optimizer will not
meet all of the goals and constraints. In these cases, optimum
performance is the best compromise solution—that is, the
solution that comes closest to satisfying each of the goals and
constraints, even though it may not completely satisfy any single
one.
Evaluation
An evaluation is an algorithm that computes a
single numerical value, which is used as the measure of
performance with respect to a design specification.
The PSpice Optimizer accepts evaluations in one of these three
forms:
• single-point Probe trace function
• Probe goal function
• PSpice Optimizer expression
Given evaluation results, the PSpice Optimizer determines
whether or not the changes in parameter values are improving
performance, and determines how to select the parameters for
the next iteration.
Trace function
A trace function defines how to evaluate a
design characteristic when running a single-point analysis (such
as a DC sweep with a fixed voltage input of 5 V).
Examples: V(out) to measure the output voltage; I(d1) to
measure the current through a component.
Refer to the online MicroSim
PSpice A/D Reference Manual
for the variable formats and
mathematical functions you can
use to specify a trace function.