User Guide

2
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8 Primer: How to Optimize a Desi
g
n
Settin
g
Up Goals and
Constraints
Before you can evaluate and improve the circuit’s performance,
you must answer these questions:
• What operating characteristics do I want to measure?
• How do the parameters affect the operating characteristics?
Once you’ve answered these questions, you are ready to:
• Set up the analyses needed to evaluate the performance
measures.
• Develop the performance measure algorithms.
• Fully define the goals and constraints in terms of these
performance measures and analyses.
Settin
g
up anal
y
ses for each
g
oal and constraint
For each specification, you must define an analysis type: AC,
DC, or transient. This is the analysis that PSpice will run to
generate results used by the PSpice Optimizer to measure
performance.
For the diode design example, you want to monitor the value of
I(D1) at a fixed input voltage of 5 V while the optimization
parameter, R1val, is varied. This means setting up a single-point
voltage sweep.
To set up a sin
g
le-point volta
g
e sweep anal
y
sis at
5 volts
1
In Schematics, from the Analysis menu, select Setup.
2
In the Analysis Setup dialog box, select the DC Sweep
check box.