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200 3. Reference Manual
calculated by a delayed rule to prevent the function ThermalVoltage to be evaluated before the
value of TEMP is known for an individual device.
Translation −> {Is −> Js*Area, Vt :> ThermalVoltage[TEMP]}
If Vt were calculated using a simple Rule (−>), ThermalVoltage would already be called at the time
of model definition, i.e. execution of the Model command.
Symbolic
Symbolic−>{symbol
, symbol
, † † † }
declare behavioral model parameters as symbolic quantities
Symbolic−>{symbol
−>alias , † † † }
Format of the Symbolic argument.
declare behavioral model parameters as symbolic
quantities and specify alias names to be used in symbolic
circuit equations
The optional argument
Symbolic is used only in conjunction with analog behavioral model definitions. It lets you specify
the subset of the model parameters declared in the Parameters section that will be treated as
symbolic quantities in a set of behavioral model equations. Model parameters which are not listed
in the Symbolic section are always replaced by their numerical values when you set up circuit
equations. This feature allows you to restrict the parameters that will appear in a system of symbolic
circuit equations to the ones you really wish to see.
The following code defines a DC model for a temperature-dependent linear resistor. The model
parameters are the nominal resistance RES, the first-order temperature coefficient TC1, the ambient
temperature TEMP, and the reference temperature TNOM. The Symbolic argument declares RES as a
model parameter which will appear in symbolic circuit equations. The other parameters will always
be evaluated numerically and will not appear explicitly in circuit equations.
Model[
Name −> "RES", Selector −> "DC",
Ports −> {"P", "N"},
Parameters −> {RES, TC1, Global[TEMP, TNOM]},
Symbolic −> {RES},
Variables −> {Voltage["P", "N"], Current["P", "N"]},
Definition −> Equations[
Voltage["P", "N"] ==
RES*(1 + TC1*(TEMP − TNOM))*Current["P", "N"]
]
]
Names of device model or instance parameters in netlists imported from external circuit simulators
with ReadNetlist sometimes have lengthy or ugly names. The alternative format of the Symbolic