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3.2 Subcircuit and Device Model Definition 203
Subcircuit[
Name −> "DifferentialPair", Selector −> "DeviceLevel",
Ports −> {"H1", "H2", "IN1", "IN2", "L"},
Parameters −> {Area, RED},
Definition −> Circuit[
Netlist[
{"Q1", {"H1" −> "C", "IN1" −> "B", "ED1" −> "E"},
Model −> "BJT", Selector −> Selector["BJT", "Q1"],
Parameters −> "LocalNPN"},
{"RED1", {"ED1", "L"}, RED},
{"Q2", {"H2" −> "C", "IN2" −> "B", "ED2" −> "E"},
Model −> "BJT", Selector −> Selector["BJT", "Q2"],
Parameters −> "LocalNPN"},
{"RED2", {"ED2", "L"}, RED}
],
ModelParameters[Name −> "LocalNPN", Type −> "NPN",
IS −> 2.*^−15, BF −> 200., RC −> 50./Area, RE −> 2./Area]
]
]
Analog Insydes allows you to implement arbitrary multi-dimensional voltage-current relations as
analog behavioral models. ABMs are implemented using sets of Equations instead of Netlist or
Circuit objects. Each model equation must be written in the form lhs == rhs, where lhs and rhs
denote arbitrary Mathematica expressions.
If you implement a behavioral model using the Equations keyword, you must declare the
unknowns of the model equations in the Variables section.
The following code implements a nonlinear DC model for a bipolar junction diode with series
resistance Rs. The first equation serves to compute the effective diode voltage vdeff. It is written in
implicit notation to demonstrate that Analog Insydes does not require model equations to be written
in explicit form var == expr, where var denotes a single symbol or branch quantity identifier.
Model[
Name −> "Diode", Selector −> "DC",
Ports −> {"A", "C"}, Parameters −> {Rs, Is, Global[Vt]},
Variables −> {Voltage["A", "C"], Current["A", "C"], vdeff},
Definition −> Equations[
Voltage["A", "C"] − Rs*Current["A", "C"] − vdeff == 0,
Current["A", "C"] == Is*(Exp[vdeff/Vt] − 1)
]
]
In addition, the
Model command lets you implement behavioral models involving ordinary differential equations