Download - Wolfram Research

50 2. Tutorial
Model[
Name −> subcircuit class name,
Selector −> selector,
Scope −> scope,
Ports −> {port nodes},
Parameters −> {parameters},
Defaults −> {defaults},
Translation −> {parameter translation rules},
Definition −> Netlist[subcircuit netlist]
]
The value of the Name argument must be a symbol which identifies an entire group, or class, of
different subcircuit implementations of a non-primitive object, such as a transistor. The value of the
Selector argument, which must also be a symbol, then selects one particular member from this
class. The Ports argument defines the port nodes of a subcircuit structure. Its value must be a list
of the identifiers of the subcircuit nodes which serve as external connection points.
Finally, the netlist of the subcircuit must be specified by means of the Definition argument. There
is no built-in limit for the nesting depth of subcircuits, so the netlist may itself contain references
to other Model definitions. However, you may only reference but not define subcircuits within
subcircuits.
Small-Signal Transistor Models
To fully understand this abstract description of the Model function, let’s examine a practical example.
Assume that we want to calculate the AC voltage transfer function of the common-emitter amplifier
from Section 2.3.1 (see Figure 3.1) and want to replace the transistor by either one of the two
small-signal equivalent circuits shown in Figure 3.2.