User Guide

Chapter 6 Analog behavioral modeling
148
Overview of analog behavioral
modeling
You can use the Analog Behavioral Modeling (ABM)
feature of PSpice to make flexible descriptions of
electronic components in terms of a transfer function or
lookup table. In other words, a mathematical relationship
is used to model a circuit segment, so you do not need to
design the segment component by component.
The part library contains several ABM parts that are
classified as either control system parts or as
PSpice-equivalent parts. See Basic controlled sources on
page 6-192 for an introduction to these parts, how to use
them, and the difference between parts with
general-purpose application and parts with
special-purpose application.
Control system parts are defined with the reference
voltage preset to ground so that each controlling input
and output are represented by a single pin in the part.
These are described in Control system parts
on page 6-153.
PSpice-equivalent parts reflect the structure of the PSpice
E and G device types, which respond to a differential
input and have double-ended output. These are described
in PSpice-equivalent parts
on page 6-174.
You can also use the Device Equations option (described
in the online OrCAD PSpice A/D Reference Manual) for
modeling of this type, but OrCAD recommends using the
ABM feature wherever possible. With Device Equations,
the PSpice source code is actually modified. While this is
more flexible and produces faster results, it is also much
more difficult to use and to troubleshoot. Also, any
changes you make using Device Equations must be made
to all new PSpice updates you install.
Device models made with ABM can be used for most
cases, are much easier to create, and are compatible with
PSpice updates.
Pspug.book Page 148 Wednesday, November 11, 1998 1:14 PM