Chapter 4  Behavioral modeling

Gnucap behavioral modeling is in a state of transition, so this is subject to change in a future release.

All simple components can have a behavioral description, with syntax designed as an extension of the Spice time dependent sources. They are not necessarily physically realizeable. Some only work on particular types of analysis, or over a small range of values. Some can be used together, some cannot.

All simple components are considered to have simple transformations. A function returns one parameter as a function of one other, as an extension of their linear behavior.

Linear behavior:
Capacitor
q = C v
Inductor
ϕ = L i
Resistor
v = I r
i = Y v
VCVS
vo = E vi
VCCS
io = G vi
CCVS
vo = E ii
CCCS
io = G ii
Sources are defined as functions of time:
Voltage source
v = f(t)
Current source
i = f(t)
For behavioral modeling / nonlinear values, replace the constant times input by an arbitrary function:
Capacitor
q = f(v)
Inductor
ϕ = f(i)
Resistor
v = f(r)
i = f(v)
VCVS
vo = f(vi)
VCCS
io = f(vi)
CCVS
vo = f(ii)
CCCS
io = f(ii)

Conditionals

AC
AC analysis only.
DC
OP
OP analysis.
TRAN
Transient analysis.
FOUR
Fourier analysis only.
ELSE
Anything not listed.
ALL
All modes.

Functions

COMPLEX
Complex (re, im) value.
EXP
Spice Exp source. (time dependent value).
FIT
Fit a curve with splines.
GENERATOR
Value from Generator command.
POLY
Polynomial (Spice style).
POSY
Posynomial (Like poly, non-integer powers).
PULSE
Spice Pulse source. (time dependent value).
PWL
Piece-wise linear.
SFFM
Spice Frequency Modulation (time dependent value).
SIN
Spice Sin source. (time dependent value).
TANH
Hyperbolic tangent xfer function.

Model Functions

TABLE
Fit a curve with splines.
Cap
Spice semiconductor “capacitor” model.
Res
Spice semiconductor “resistor” model.