Electronic – Digitally Controlled Variable Capacitor

capacitorintegrated-circuit

I'm working on a simple circuit where I have to vary the capacitance across two pins of an IC in the run time. Right now, I use 6 capacitors from 0.001uF to 1uF and switches between them manually using sticky push buttons. I could use a gang capacitor and vary the value by turning a knob. But I think using some digital controls will be a bit more smarter, such as I replace presets with digital potentiometers like this one. Is there any off-the-shelf digitally controlled capacitor ICs? Is there any work-around for this by using some other components?

Update: The following is the circuit I'm working with. I need to replace the external timing capacitor C with a digitally controlled variable capacitor.
enter image description here

Best Answer

You could use a FET bus switch, like the SN74CBT3125, however this will add about 5 ohms resistance in series with each capacitor. If that is a problem, you could always use reed relays like this one, each driven by a FET or BJT transistor, which would exactly emulate your current arrangement with the pushbuttons.