These diodes have the capacities variable depending on the value of the reverse bias voltage applied between the anode and the cathode. They are also called VCDs (Variable Capacitance Diodes) or VariCaps. They are used in radio-frequency matching circuits for electronic tuning.
They are particularly optimum for switching UHF/VHF frequency band of TV tuners.
Making use of rectifying property brought about by contact of a metal and a semiconductor, in place of P-N junction, these diodes are activated by a majority carrier. They are suitable for radio-frequency signal mixer circuits because the forward voltage is low and the reverse recovery time is short.