A CMOS signal processing unit for silicon photodiode detectors

The paper presents a CMOS signal processing unit to use with silicon photodiodes for low energy gamma and X-ray detection. The unit consists of a preamplifier, an amplifier and a comparator for nuclear pulse signal shaping, amplification, and discrimination. The unit is fabricated by the standard 0.5 μm double-poly double-metal (DPDM) CMOS integrated-circuit process and has a chip size less than 80 μm × 50 μm. The amplifier is basically a CMOS inverter, which has the merits of simple structure and low power consumption. The amplifier section has a voltage gain up to 85 dB in the interested frequency range of 10 to 100 kHz. The unit is operated under a single supply voltage of 3 volts and has a power consumption less than 100 μW. Sensitivity studies indicated a satisfactory performance under the uncertainties in manufacturing process and the fluctuations of operating temperature and supply voltage.