The Design Of The Charge Sensitive Amplifier For TopMetal2_ Chip

With particle detectors widely have applied in the field of high energy physics, nuclear medicine and mineral analysis etc.st, the new type of particle detector has attracted more and more attention, and the weak signal output by the detectors need to be amplified and shaped,so it can be processed by the next stage circuit. So the charge sensitive preamplifier plays an important role in the detector’s readout circuit. As the front-end readout circuit, charge sensitive preamplifier directly affects the performance of the readout circuit. And its noise performance determines the minimum input charge which the chip can handle. Therefore, it’s very helpful to study the charge sensitive preamplifier thoroughly to improve the performance of the readout circuit.The main content of this paper is to design a charge sensitive amplifier for TopMetal2-pixel detector chip. TopMetal2_ chip take the topmetal as electron collector, which pixel area is 83.2um×83.2um and the pixel array is 72×72,it can achieve a two-dimensional spatial measurement of the electron, therefore TopMetal2_ chip has high space resolution, combining with the CdZnTe crystal can be used as CdZnTe detector. The detector can be applied in CT, Ion beam measurement etc, the results show it has high-precision.TopMetal2_ chip is a chip to realize the detection of single electron detection as the ultimate goal and the design index of the equivalent noise charge is 30e, it has put forward higher request to the design of charge sensitive preamplifier. The TopMetal2_chip is based on the x-fab 0.35um process, the software is CadenceIC5141 Virtuoso and the simulator is spectre. The charge sensitive preamplifier adopts the fold cascode structure and the simulation results show that the amplifier’s gain is 73dB,the power supply rejection ratio is 85dB,common mode suppression ratio is 95dB,the power dissipation is luA,the area is 51.1um×21.1um and the equivalent noise charge is 23e, basically achieved the expected design goals.This article first introduces the kinds and the application of detectors and the TopMetal2- chip, and introduces the foundation of IC design, then analyzes the charge sensitive amplifier noise distribution and the optimization method. According to the design requirements, we propose the specific realization of the circuit, and give the parameters and the results and complete the layout of the circuit. Finally, we test the analog output of the chip. The test results show that the performance indexes meet the design requirements.