All nMOS 10-T AQRC for Monolithic Chlorophyll Fluorescence SPAD Sensor

Development of monolithic all nMOS Automatic Quenching and Reset Circuit (AQRC) for chlorophyll fluorescence SPAD sensor is reported using Microwind 3.1 and LTSpice version IV for 120 nm technology. An efficient bio-signal acquisition with single-photon counting facility, fast quenching, and reset is described using only ten nMOS transistors. The uniqueness of the design ensures a minimum dead time of 1 nS between adjacent incident photons. This corresponds to a maximum attainable count rate of 1000 MCounts/sec, not previously reported. The power dissipation is low (20-mW standby), making the circuit an ideal candidate for portable instruments. This is the first of its kind complete monolithic nMOS AQRC reported ever with better features than its CMOS counterparts.