Variable Resistor with Constant Capacitor

Purpose

Controlled resistance in parallel with constant capacitance

Library

Electrical / Passive Components

Description

This component models a variable resistor with a constant capacitor connected in parallel. The resistance is determined by the signal fed into the input of the component. It may not be set to zero.

Note

In this component the resistor is implemented as a voltage-dependent current source. Without the parallel capacitor, which fixes the momentary voltage, this would result in an algebraic loop. Therefore, the capacitance may not be set to zero.

Parameters

Capacitance

The value of the capacitor, in farads (\(\mathrm{F}\)). All finite positive and negative values are accepted, excluding 0. The default is 100e-6.

In a vectorized component, all internal capacitors have the same value if the parameter is a scalar. To specify the capacitances individually use a vector \(\left[ C_1\; C_2 \ldots C_n\right]\). The length \(n\) of the vector determines the width of the component.

Initial voltage

The initial voltage of the capacitor at simulation start, in volts \((\mathrm{V})\). This parameter may either be a scalar or a vector corresponding to the width of the component. The positive pole is marked with a “+”. The initial voltage default is 0.

Probe Signals

Capacitor voltage

The voltage measured across the capacitor, in volts \((\mathrm{V})\). A positive voltage is measured when the potential at the terminal marked with “+” is greater than the potential at the unmarked terminal.