A gating circuit switches the responsivity of a photomultiplier tube between ON and OFF states by modulating the voltage bias of the one or more of its electrodes. The gating circuit capacitively couples a voltage pulse to the photocathode or other electrode of the photomultiplier tube in response to a low-voltage gating triggering signal. The voltage divider network and high-voltage power supply used to statically bias the photomultiplier tube also power the gating circuitry and source the gating voltage pulse, thus circumventing the need for a separate high-voltage power supply. The gating circuit represents a near-inconsequential burden on the power supply, as it draws practically negligible current from the voltage divider network. The electrode gating pulse characteristics, including rise- and fall-times, voltage swing amplitude and duration, can be modified by adjusting resistor and capacitor values and Zener diode characteristics of the gating circuit and voltage divider network. The circuit can also be used to gate related devices such as microchannel plates and image intensifiers.