Current-mode front-end electronics for silicon photo-multiplier detectors

Silicon photo-multiplier (SiPM) detectors represent an attractive solution for the detection of low energy photons in several fields of both high energy physics and medical imaging. Here we review a recently proposed electrical model for this kind of detectors, which can be conveniently used to perform reliable simulations at circuit level and allows to reproduce accurately the waveform of the signal generated by the SiPM when coupled to the front-end electronics. This is particularly useful in order to choose the most suitable front-end architecture for SiPM detectors. In particular, we propose a front-end architecture based on a current buffer as input stage, featuring small input impedance and large bandwidth due to the use of a current feedback. Moreover the current-mode approach enhances the dynamic range as it does not suffer from possible voltage limitations due to deep-submicron implementations. Two alternative circuit solutions have been designed and manufactured in a 0.35 mum CMOS process. We report the first measurement results obtained by coupling the two prototypes to a SiPM detector excited by a pulsed infrared laser. The measurements allow to validate the functionality of the proposed front-end architecture and demonstrate its capability of managing large current signals with good linearity.