A Multi-Channel Front-End ASIC for Pixellated Detectors

A 16-channel front-end ASIC is designed for pixellated detectors. It consists of a charge-sensitive-preamplifier(CSA), a CR-(RC)² shaper and a class-AB buffer for each channel. A novel continuous reset scheme for low noise and large linear range is presented. The equivalent feedback resistance can be digitally programmed by 3 decades. The shaper output width can also be adjusted from 1mus to 10mus, allowing it to be used both for low noise and high counting rate applications. The chip is implemented in 0.6mum CMOS process. The ENC is measured to be 1413e+20e/pF @ 1mus pulse width and 1402e+11e/pF @ 10mus pulse width respectively. The large zero-capacitance ENC is dominant by the FETs used as resistors in the shaper. The nonlinearity is less than 1.1% over an input charge range of 0-28fC using 0.1pF feedback capacitor.