Created by Created May 10, 2012 Last modified May 10, 2012 Tags

### Summary

Another way to make a behavioural capacitor where the capacitance is programmable by the voltage on the 'capacitance' net.
A 1uF capacitor is shown for reference.

Simulates OK (Same as behavioural capacitor 02 but fixed by adding Rpar1 = 1G across I1).

### Description

Another way to make a behavioural capacitor where the capacitance is programmable by the voltage on the 'capacitance' net. A 1uF capacitor is shown for reference.

Changing the expression to V(int1)/(I(R2.nA) would allow the capacitance to be programmed by the current in R2.

The expression can be scaled. For example:

V(int1)/(1u*V(capacitance))


would produce a 1uF capacitor with a V(capacitance) of 1V rather than 1uV.

BEWARE! A negative value of control parameter will produce a negative capacitance. Adding an ABS() function will prevent this:

V(int1)/ABS(V(capacitance))

Simulates OK.

For more see: SPICE Analog Behavioral Modeling of Variable Passives by Christophe Basso http://powerelectronics.com/mag/power_spice_analog_behavioral_2/