User Guide

Using global parameters and expressions for values
67
Using global parameters and
expressions for values
In addition to literal values, you can use global parameters
and expressions to represent numeric values in your
circuit design.
Global parameters
A global parameter is like a programming variable that
represents a numeric value by name.
Once you have defined a parameter (declared its name
and given it a value), you can use it to represent circuit
values anywhere in the design; this applies to any
hierarchical level.
Some ways that you can use parameters are as follows:
• Apply the same value to multiple part instances.
• Set up an analysis that sweeps a variable through a
range of values (for example, DC sweep or parametric
analysis).
Declaring and using a global parameter
To use a global parameter in your design, you need to:
• define the parameter using a PARAM part, and
•
use the parameter in place of a literal value
somewhere in your design.
W
h
en mu
l
tip
l
e parts are set to t
h
e same
value, global parameters provide a
convenient way to change all of their
values for “what-if” analyses.
Example: If two independent sources have
a value defined by the parameter
VSUPPLY, then you can change both
sources to 10 volts by assigning the value
once to VSUPPLY.
Pspug.book Page 67 Wednesday, November 11, 1998 1:14 PM