Time Correlated Single Photon Counting (TCSPC) is a widely diffused technique used in scientific experiments requiringthe analysis of optical pulses with high timing precision. One of the major limitations affecting this tool are distortionphenomena at high count rates happening due to pile-up. As a result, experiments must be carried out at a slower operatingrate than the laser excitation frequency (1%-5%). It has been recently demonstrated that matching the detector dead timewith the duration of the laser excitation period allows to overcome the aforementioned speed limitation, while still keepingdistortion low. Theoretical results envision a speed improvement by almost an order of magnitude. In this work we presentdedicated integrated electronics to implement the proposed idea. The selected detector for this design is a customtechnology SPAD in order to achieve high performance. The SPAD is externally driven by an Active Quenching Circuit(AQC) that senses the avalanche current and provides a prompt quenching and reset of the detector. The AQC features afinely tunable dead time and a low reset time, two key aspects to achieve a very-low distortion regime and high efficiency.The detector electric signal is read out by a fully differential pick-up circuit, delivering a timing differential signal withpicosecond precision and rejecting disturbances thanks to a dummy cell. A fast time-to-amplitude converter is used tomeasure the time of arrival of the photons with picoseconds precision and high linearity.
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