Design Of High Precision Charge-sensitive Amplifier For SiC Detector

In the field of nuclear detection,silicon carbide detector has been widely studied by virtue of its high temperature and irradiation resistance.In the nuclear detection application scenario,conventional semiconductor detectors are gradually replaced.Compared with conventional semiconductor detectors,silicon carbide detectors have larger junction capacitance,smaller output signal and shorter duration,which requires higher precision design of charge sensitive amplifiers.The existing circuit built by discrete devices has a bottleneck in performance improvement,but the fully integrated circuit has great potential to be tapped.Therefore,it is of great significance to study the design technology of charge sensitive amplifier with high charge sensitivity and low noise by using silicon based total integration technology in the application scenarios of Si C detector.In this thesis,the application background of the subject is first introduced,and the advantages and disadvantages of silicon carbide detector and other irradiation detectors are compared.Then according to the application scenario of silicon carbide detector,the specific requirements of high precision design of charge sensitive amplifier are put forward.Aiming at high-precision design,the working principle of charge-sensitive amplifier and the influence of input capacitance on circuit are analyzed in detail,and the design scheme of each sub-module in high-precision circuit is clarified,including:Gain-Boost technology is adopted to increase the dc gain of the operational amplifier and reduce the charge signal loss caused by large input capacitance;The equivalent resistance value of negative feedback structure is increased to reduce ballistic loss.Finally,a charge-sensitive amplifier is designed which can amplify signals with high accuracy at 1p F input capacitance.In addition,considering the extreme case of circuit performance deterioration after irradiation,redundancy design is reserved in this design.Based on silicon 0.18μm BCD process,the circuit design and layout of the high-precision charge-sensitive amplifier are completed.The simulation results show that the designed charge-sensitive amplifier can work stably in the environment of 0～70℃.Under the typical application of1p F input capacitor,the charge sensitivity is up to 140.8m V/f C,and the equivalent noise charge is up to 25e~-.The static current is about 203μA,which can withstand 2%of the power ripple variation,reaching the expected design index,and providing an important chip support for nuclear detection system.