This chapter describes the modeling of nullor-based active devices from the
circuit level of abstraction. After a brief overview on the nullor concept and its
properties, the modeling of active devices not only at the voltage-mode but also at the
current-mode and the mixed-mode of operation from two-port and four-terminal network
point of view is described in some detail. An important view that permeates the chapter
is that the nullor-based models are not too complex and they can be introduced in CAD
tools. Furthermore, parasitic elements can easily be added in order to predict their impact
on the final response of the circuit. Several examples using nullor-based models
illustrate its use to calculate fully-symbolic small-signal characteristics of linear or
linearized analog circuits.
Keywords: Symbolic analysis, nodal analysis, modified nodal analysis, nullor, pathological elements,
operational amplifiers, current mirrors, analog signal processing, controlled sources, stamps.
