A power-efficient, low-noise, wideband, integrated CMOS preamplifier for LSO/APD PET systems

A power-efficient, low-noise, wideband, 0.8-mu CMOS charge-sensitive preamplifier has been designed and optimized for LSO/APD based PET systems. Low-noise, wideband performance is needed to achieve I-ns FWHM timing resolution available from LSO/APD detectors, and power efficiency is needed since thousands of preamplifiers are required in a LSO/APD based PET tomograph. A methodology for optimizing wideband timing performance is presented to minimize dominant, frequency-turn-up, input-noise current associated with input noise voltage and total capacitance at the input. The methodology suggests the use of a nMOS input device operating in moderate inversion for high transconductance and low input white-noise voltage consistent with moderate input capacitance. Measured preamplifier input-referred, white-noise voltage is 0.65 nV/root Hz and risetime is 6 ns (58 MHz 3-dB bandwidth). Measured timing resolution is 1.15 ns FWHM and energy resolution is 12.1% FWHM for 511-keV gamma rays detected by a 4 x 4 x 10 mm LSO crystal coupled to an APD. Measurements include the APD capacitance of 30 pF and are obtained at a preamplifier input-device current of only 2 mA.