User Guide

Chapter 8 DC analyses
216
Overview of DC sweep
The DC sweep analysis causes a DC sweep to be
performed on the circuit. DC sweep allows you to sweep
a source (voltage or current), a global parameter, a model
parameter, or the temperature through a range of values.
The bias point of the circuit is calculated for each value of
the sweep. This is useful for finding the transfer function
of an amplifier, the high and low thresholds of a logic gate,
and so on.
For the DC sweep analysis specified in Figure 56, the
voltage source V1 is swept from -0.125 volts to 0.125 volts
by steps of 0.005. This means that the output has
(0.125 + 0.125)/0.005 +1 = 51 steps or simulation points.
A source with a DC specification (such as VDC or IDC)
must be used if the swept variable is to be a voltage type
or current source. To set the DC value, select Properties
from the Edit menu, then click on the cell under the DC
column and type in its value.
The default DC value of V1 is overridden during the DC
sweep analysis and is made to be the swept value. All of
the other sources retain their values.
After running the analysis, the simulation output file
(EXAMPLE.OUT for the EXAMPLE.OPJ circuit in
Figure 56) contains a table of voltages relating V1, node
OUT1, and node OUT2.
Pspug.book Page 216 Wednesday, November 11, 1998 1:14 PM