A CMOS 0.13µm low power front-end for GEM detectors

A low power front-end for GEM (Gas Electron Multiplier) detectors has been developed in 0.13µm CMOS node. The front-end sensitivity is 0.5mV/fC which remains almost unchanged up to a 15 pF detector parasitic capacitance. The input dynamic charge range varies from 30fC to 1pC including only a single (negative) polarity charge. The front-end provides as output signal two different time-domain square-wave signals. The first one indicates the charge detection event and the second one the amount of charge (providing a time-domain impulse, whose duty-cycle is proportional to the effective charge read by the front-end). Proper automatic calibration circuits are then implemented in order to optimize the front-end performance in case of CMOS process and temperature variations. The power consumption is 3.8mW, against 12mW in the existing market solutions [9]. A feed-forward opamp architecture has been exploited in analog part of read-out channel, in order to improve speed and time-response slope.