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66 2. Tutorial
B
C
E
RB
gm*VBE
E
Figure 3.4: Transistor model with voltage-controlled current source
Although the global subcircuit database still contains a definition of NPNTransistor/ACsimple we
can safely use the same name and selector for a local subcircuit without changing the global definition,
provided we specify Scope −> Local. Upon subcircuit expansion, Analog Insydes first looks
for a local subcircuit with the requested name and selector. The global definition is retrieved only if
no matching local definition is present.
In[24]:= darlWithLocalModel =
Circuit[
Netlist[
{I1, {0, 1}, 1},
{Q1, {1 −> "B", 2 −> "C", 3 −> "E"},
Model −> NPNTransistor, Selector −> ACsimple},
{Q2, {3 −> "B", 2 −> "C", 0 −> "E"},
Model −> NPNTransistor, Selector −> ACsimple},
{Load, {0, 2}, Type −> Resistor, Value −> RL,
Pattern −> Impedance}
],
Model[
Name −> NPNTransistor,
Selector −> ACsimple,
Scope −> Local,
Ports −> {"B", "C", "E"},
Parameters −> {RB, gm},
Definition −>
Netlist[
{RB, {"B", "E"}, RB},
{VC, {"B", "E", "C", "E"}, gm}
]
]
];
Now, ExpandSubcircuits will use the local definition of NPNTransistor/ACsimple. The global
definition has not been altered, as we can see by expanding the netlist of the Darlington amplifier
from Section 2.3.5 (see Figure 3.3) without models again.