Riordan's circuit simulating capacitance

[nickagian]

Hi!

I have implemented the Riordan's circuit and chosen the impedances in such a way so as to create a large equivalent capacitance with a value that is controlled by the value of a trimmer. It is actually a capacitance multiplier. I intend to use this circuit in an LC network in order to be able to shift its resonance frequency. However I'd like to analyse the circuit alone before I connect it with the LC network.

How is it possible to measure the equivalent capacitance value? Theoretically I should measure the magnitude of the voltage applied and current through the circuit and the phase difference between them. But practically this is quite difficult. Is there any other way perhaps to do this?

 

[BradtheRad]

Find a way to measure the capacitive time constant in various situations.

Examples:

* How long does it take to charge and discharge 63 percent of the way, when subjected to a pulse through a known resistance? This will give you the capacitive time constant.

* How well does it pass AC sinewaves at various frequencies? A formula will tell you the capacitance.

* What frequency does it produce in a single-capacitor oscillator? There are formulae to tell you the capacitance.

* How long will it light an led through an appropriate current-limiting resistor? (This is not too different from the first test above.)

If the capacitor is really large, then it tends to need higher current (or lower series resistance) if you want things to happen quickly while you're watching.