User Guide
Phase Two: Settin
g
Up the Optimization 2
-9
a
To fix the voltage of V1, fill in the DC Sweep dialog
box as shown.
b
Click OK to return to the Setup Analysis dialog box.
c
Select the DC Sweep check box to enable it.
3
Clear all other analysis check boxes.
4
Click OK.
Developin
g
performance measures
To measure performance you must define an evaluation
algorithm for each specification. There are three alternatives:
• trace function (for single-point simulations)
• Probe goal function
• PSpice Optimizer expression
When the evaluation is anything other than a single-point
simulation or PSpice Optimizer expression, you must develop
Probe goal functions to derive values from the simulation
results. Developing goal functions is an iterative process that
involves writing the goal function, simulating the design, and
testing the goal functions against actual results to make sure you
are measuring the waveform characteristics you intended.
A Probe goal function is not required for the diode design
example. You are examining the trace of R1Val versus I(D1)
which shows the relationship between the value of R1 and the
diode forward current. Because only a single point on the curve
is of interest, the trace function, I(D1), is the appropriate
evaluation.
The DC Sweep settin
g
s are:
Swept Var Type = Volta
g
e
Source
Sweep Type= Value List
Name = V1
Values = 5v
See Evaluation on page 1-9 and
the sections that follow for a
definitions of trace function,
Probe
g
oal function, and PSpice
Optimizer expression.
MicroSim supplies standard
g
oal
functions for AC, DC, and
transient analyses in the file
msim.prb. This file resides in the
MicroSim root directory. You can
add
g
oal functions to this file, or
create a local .prb file for use
with a specific desi
g
n.
See
Chapter 7,Tutorial: Using
Constrained Optimization (MOS
Amplifier) for examples of
Probe
g
oal functions used to
evaluate performance.
Refer to your PSpice user’s
g
uide for instructions on creatin
g
g
oal functions, and for a
description of the
g
lobal and
local .prb files.