User`s guide

11
-
18 Transient Analysis
Switchin
g
Circuits in
Transient Anal
y
ses
Running transient analysis on switching circuits can lead to long
run times. PSpice A/D 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.
Plottin
g
H
y
steresis
Curves
Transient analysis can be used to look at a circuit’s hysteresis.
Consider, for instance, the circuit shown in Figure 11-4 (netlist
in Figure 11-5).
Fi
g
ure 11-4
ECL Compatible Schmitt Trigger
This technique is described in:
V. Bello, “Computer Pro
g
ram
Adds SPICE to Switchin
g
-
Re
g
ulator Analysis,” Electronic
Desi
g
n , March 5, 1981.