Capacitance controlled by signal
Electrical / Passive Components
This component models a variable capacitor. The capacitance is determined by
the signal fed into the input of the component. The current through a variable
capacitance is determined by the equation
C v +C
Since v is the state variable the equation above must be solved for
control signal must provide the values of both C and
Cin the following
.It is the responsibility of the user to
provide the appropriate signals for a particular purpose (see further below).
If the component has multiple phases you can choose to include the capacitive
coupling of the phases. In this case the control signal vector must contain the
elements of the capacitance matrix (row by row) and their derivatives with re-
spect to time. The control signal thus has a width of 2 n
,n being the number
Note The momentary capacitance may not be set to zero. Incase of coupled
capacitors, the capacitance matrix may not be singular.
There are two common use cases for variable capacitors, which are described
in detail below: saturable capacitors, in which the capacitance is a function of
the voltage and electrostatic actuators, in which the capacitance is a function
of an external quantity, such as a capacitor with movable plates.
Saturable Capacitor Modeling
When specifying the characteristic of a saturable capacitor, you need to distin-
guish carefully between the total capacitance C
(v) = Q=v and the differen-
tial capacitance C
(v) = dQ=dv.