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2.3 Circuits and Subcircuits 63
In[18]:= Circuit[
Netlist[
{I1, {0, 1}, 1},
{Q1, {1 −> "B", 2 −> "C", 3 −> "E"},
Model −> NPNTransistor, Selector −> ACsimple,
RB −> RB1, beta −> 150},
{Q2, {3 −> "B", 2 −> "C", 0 −> "E"},
Model −> NPNTransistor, Selector −> ACsimple,
beta −> beta2},
{Load, {0, 2}, Type −> Resistor, Value −> RL,
Pattern −> Impedance}
],
Model[
Name −> NPNTransistor,
Selector −> ACsimple,
Ports −> {"B", "C", "E"},
Parameters −> {RB, beta},
Definition −>
Netlist[
{RB, {"X", "E"}, RB},
{CC, {"B", "X", "C", "E"}, beta}
]
]
] // ExpandSubcircuits // DisplayForm
Out[18]//DisplayForm=
Netlist Flat, 6 Entries:
I1, 0, 1, 1
RB$Q1, X$Q1, 3, RB1
CC$Q1, 1, X$Q1, 2, 3, 150
RB$Q2, X$Q2, 0, RB$Q2
CC$Q2, 3, X$Q2, 2, 0, beta2
Load, 0, 2, Type Resistor, Value RL, Pattern Impedance
During subcircuit expansion, the model parameters have now been replaced by the values from the
top-level netlist. As we did not assign a value to the base resistor of Q2, the automatic instantiation
mechanism has created the symbol RB$Q2 in order to provide a default value for RB.
2.3.6 The Scope Argument
Local and Global Subcircuit Definitions
In all the preceding examples, the top-level netlist is immediately followed by the definitions of
the subcircuits referenced from within the netlist. These subcircuit definitions are local and volatile
because they are neither visible outside the scope of the enclosing Circuit statement nor do they
"survive" subcircuit expansion. When doing multiple circuit analyses with a number of frequently
used device models it would be rather tedious if we always had to include all potentially selected
models in the circuit description together with the top-level netlist. Therefore, we have the option to
make any subcircuit definition permanent and accessible from within other netlists by providing an