User Guide

6
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6 Tutorial: Explorin
g
Desi
g
n Tradeoffs (Active Filter)
Tweakin
g
Parameters
Once the derivatives are calculated, you can use the PSpice
Optimize to explore how small changes in the parameters affect
the performance of the design.
To examine the performance effect when
chan
g
in
g
aGain from 0.5 to 0.4
1
Highlight the current value for aGain, and type 0.4.
2
Press J.
The value of the Gain specification changes from the initial
value of 14.811 to a new value of 13.825. The target is 10.0,
which is a change in the right direction.
Center frequency and bandwidth also change. In the case of
center frequency, the change from its initial value of 8.322
to a new value of 8.298 is in the wrong direction.
This frequently occurs. You can try various strategies to get
closer to the target values. Two common approaches are:
• Adjust a given parameter to get the best results, then
vary the other parameters.
Example: Continue to adjust aGain until you are
satisfied with the performance. Then incrementally
change Fc until you are satisfied. And finally, change
BW.
• Change every parameter in the set by a small amount at
a time, and continue in this manner to get the best
results.
Example: Adjust aGain once by a small amount, then
Fc, then BW. Continue with this pattern of adjustments
until you are satisfied.
new parameter
updated
g
oal values
value