A low-power analog front-end amplifier for SiPM based radiation detectors

A low-power analog front-end amplifier for SiPM based radiation detectors is presented. In particular, an event-driven low-noise charge sensitive amplifier (CSA) is developed in conjunction with a novel charge division scheme by capacitively coupling the SiPM to the CSA so that the SiPM’s linear energy-charge correlation is preserved, while conserving power. Following extensive circuit simulations and design finalization, a test chip containing the presented front-end amplifier has been fabricated in the target 65 nm CMOS technology. The fabricated prototype and the presented SiPM read-out approach have been verified and characterized using a dedicated test setup. An energy resolution of 11.7% is achieved for the 511 keV peak of a Na-22 source and 10.9% for the 662 keV peak of a Cs-137 source, using an onsemi 3 mm × 3 mm SiPM and a LYSO scintillator coupled to the fabricated CSA. The front-end amplifier consumes 350 μW of power, while maintaining linearity across a wide energy range following calibration. Including the active amplifier circuitry, the bias generator section, and the capacitor bank that realizes the feedback capacitor Cfb of the CSA, the front-end amplifier occupies a silicon area of 50,000 μm2, which supports low-power, multi-channel read-out realizations within a small footprint.