A Study Of A Readout Circuit Used For CZT Pixel Arrays Nuclear Radiation Detector

With the development of nuclear technology, the application area of nuclearmaterial is also expanding. Nuclear radiation of high energy is harmful to people’shealth. In order to avoid this hurt, it is necessary to have detection on nuclear radiation.CZT detector is a new type of room temperature semiconductor detector. Compared totraditional detectors, it is better at detection efficiency, detection range, energyresolution, and it is working at room temperature. So it has been widely used in nuclearradiation detection.In order to deal with the weak electric charge signal of CZT nuclear radiation pixelarray detector, based on the GPDK0.18μm,1.8V process model, this paper designed aCMOS analog read out circuit and A/D converter, lay the foundation for single chipintegration of nuclear radiation a pixel array detector.Firstly, a charge-sensitive preamplifier is designed according to output signal’scharacteristics of the CZT detector. The amplifier’s function is converting CZTdetector’s charge output signal to voltage signal. Secondly, in view of the charge signalextracted from CZT detector by charge-sensitive preamplifier is very weak, designed atwo-stage inversed proportional operational amplifier to linearly amplify the weakvoltage signal to reduce performance requirements of the followed processing circuits.Considered of the load driving capability of preamplifier, the magnification of first stageoperational amplifier is2and is smaller than the magnification of second stageoperational amplifier. Thirdly, the paper designed a correlated double sampling circuitwith single capacitance to filter noise. Compared to traditional correlated doublesampling circuit, the circuit has less sampling capacitor and greatly saved local circuitchip area. Finally, designed a10bit pipelined ADC to digitalize analog signal forfollowed processor’s convenience on digital processing. The pipelined ADC consists of1.5bit/stage sub pipelined stage,2bit flash-ADC, delayed units and a digital correctionunit. It can quickly and accurately convert analog signals into corresponding binarydigital signals and consume moderate layout area.After the simulation of Spectre in Cadence, it showed that:①The energy range ofdesigned readout circuit which can treat with incident rays is form100keV to500keV;②The designed readout circuit is able to extract the output charge signal of CZTdetector and linearly amplify signal, filter the noise in signals, convert the analog signals to digital signals;③The power consumption of the designed readout circuit isless than5mW, the layout area is1325×970μm~2. Lay the foundation of single chipintegration of CZT nuclear radiation pixel array detector.