Noise performance of the charge sensitive amplifier for photodetection

An integrated circuit for charge sensitive amplifier (CSA) was developed for X-ray detection. The circuit has been optimized for reading signals from silicon strip detectors with few pF input capacitance for low power and low noise. Theoretical calculations and optimizations are presented and compared with experimental results. Noise as low as 237 ENC [electrons] was obtained including a silicon detector of 1.3 pF and 0.386 pA of leakage. The power consumption was less than 100 W. Other circuit parameters were also obtained from experiments. The circuit was fabricated in standard 0.25 um CMOS technology and the circuit occupies an area of 4 mm times 4 mm.