Design of passive-quenching active-reset circuit with adjustable hold-off time for single-photon avalanche diodes

摘要

Single-photon avalanche diodes (SPADs) are gaining popularity in applications where low intensity light needs to be detected. Since they are used in Geiger mode, where the self-sustaining avalanche needs to be quenched, an important part of the detection circuitry is the quenching circuit. First, we examine the operation of a basic passive quenching circuit consisting of the SPAD and two series resistors and measure the SPAD's dark count rate. Then we implement a passive quenching circuit with active reset (PQAR). Without a sufficiently long hold-off time between quenching and reset the circuit does not operate properly. Because of that, a hold-off time is introduced by means of an adjustable time delay circuit. The behavior of the PQAR circuit for different hold-off times is then examined, and the minimum hold-off time of 1 μs, which still allows for correct operation with the given circuitry is determined. Finally, a comparison is made between the passive and the PQAR circuit, focusing on the advantages of active over passive reset.