Low noise multi-channel readout front-end in 0.35 μm CMOS process for APD-based PET detectors

A low-noise multi-channel charge-sensitive preamplifier (CSA), designed in AMS 0.35 μm CMOS process, is presented for both its theoretical analysis and its CAD simulation. It is foreseen to be used as front end readout electronics of Avalanche Photo Diodes (APD) dedicated to a small animal Positron Emission Tomography (PET) system. The CSA reads charge signals (10 bits dynamic range) from an APD array having 10 pF of capacitance per pixel. A linearized degenerated differential pair which ensures high linearity in all dynamical range is used as the high feedback resistor for preventing pile up of signals. The designed CSA has the capability of compensating automatically up to 40 nA leakage current from detector. An equivalent input noise charge of 330 e- rms has been obtained from simulation for a 10 pF detector capacitance and 40 nA leakage current.