A high-speed, low-noise CMOS 16-channel charge-sensitivepreamplifier ASIC for APD-based PET detectors
Description: A high-speed, low-noise 16-channel amplifier IC has beenfabricated in the HP 0.5 mm CMOS process. It is a prototype for use witha PET detector which uses a 4x4 avalanche photodiode (APD) array having 3pF of capacitance and 75 nA of leakage current per pixel. Thepreamplifier must have a fast rise time (a few ns) in order to generatean accurate timing signal, low noise in order to accurately measure theenergy of the incident gamma radiation, and high density in order to readout 2-D arrays of small (2 mm) pixels. A single channel consists of acharge-sensitive preamplifier followed by a pad-driving buffer. Thepreamplifier is reset by an NMOS transistor in the triode region which iscontrolled by an externally supplied current. The IC has 16 differentgain settings which range from 2.085 mV/fC to 10.695 mV/fC. The gain isdetermined by four switched capacitors in the feedback loop. The switchstate is set by two digital input lines which control a 64-bit shiftregister on the IC. A preamplifier 10-90 percent rise time as low as 2.7ns with no external input load and 3.6 ns with a load of 5.8 pF wasachieved. For the maximum gain setting and 5.8 pF of input load, theamplifier had 400 electrons of RMS noise at a peaking time of 0.7 us. TheIC is powered by a +3.3 V supply drawing 60 mA.
Date: December 2, 2002
Creator: Weng, M.; Mandelli, E.; Moses, W.W. & Derenzo, S.E.
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