Active-Quenching and Gating Circuits for Single-Photon Avalanche Diodes (SPADs)

Single-photon detection by avalanche photodiodes with uniform breakdown over the junction area (single--photon avalanche diodes SPADs) is well known. The active quenching method, introduced by the authors, has been shown to avoid drawbacks of passive-quenching circuits and provide accurate operation of the devices. New active-quenching circuits are here presented. Dead times below 20 ns are obtained. A fast gating control acting directly on the photodetector has been developed, in view of timing studies with closely-spaced ultrashort light pulses.