User Guide

Chapter 10 Transient analysis
266
Switching circuits in transient
analyses
Running transient analysis on switching circuits can lead
to long run times. PSpice must keep the internal time step
short compared to the switching period, but the circuit’s
response extends over many switching cycles.
One method of avoiding this problem is to transform the
switching circuit into an equivalent circuit without
switching. The equivalent circuit represents a sort of quasi
steady-state of the actual circuit and can correctly model
the actual circuit’s response as long as the inputs do not
change too fast.
Plotting hysteresis curves
Transient analysis can be used to look at a circuit’s
hysteresis. Consider, for instance, the circuit shown in
Figure 65 (netlist in Figure 66).
Figure 65 ECL-compatible Schmitt trigger.
T
h
is tec
h
nique is
d
escri
b
e
d
in:
V. Bello, “Computer Program Adds SPICE to
Switching-Regulator Analysis,”
Electronic Design, March 5, 1981.
Pspug.book Page 266 Wednesday, November 11, 1998 1:14 PM