基于阻容低通反馈的电荷灵敏前置放大器的设计  

Design of charge sensitive preamplifier based on RC low pass feedback

作　　者：容易 曾国强[1] 葛良全[1] 胡传皓 何黎[1] 侯杨 李欣池 RONG Yi;ZENG Guoqiang;GE Liangquan;HU Chuanhao;HE Li;HOU Yang;LI Xinchi(Applied Nuclear Technology in Geosciences Key Laboratory of Sichuan Province,Chengdu University of Technology,Chengdu 610059,China)

机构地区：[1]成都理工大学地学核技术四川省重点实验室

出　　处：《核技术》2019年第9期37-41,共5页Nuclear Techniques

基　　金：国家重点研发计划项目(No.2017YFC0602100);国家自然科学基金(No.41474159)资助~~

摘　　要：传统电荷灵敏前置放大器以高阻值电阻作为低频反馈端,高阻值电阻所引入的热噪声为前置放大器噪声的主要来源。本文以N沟道结型场效应晶体管和阻容(Resistor-Capacitance,RC)电路构成低通网络代替传统高阻值反馈电阻完成了新型电荷灵敏前置放大器的研制。该电路以结型场效应晶体管和集成运算放大器构成放大电路,具有高输入阻抗及大开环增益的优点;以小容值电容构成高通回路,为电路提供高频反馈回路,同时实现核脉冲电流的积分;以RC低通网络构成直流反馈回路,为电路提供一个稳定的直流工作点,同时构成电压分压器使N沟道结型场效应管工作在正向偏置状态,实现对反馈电容中的电荷进行连续放电。相比于传统阻容反馈式电荷灵敏放大器,该电路能够有效克服大阻值反馈电阻引入的噪声,尤其适用于Si-PIN等半导体探测器。将该电荷灵敏前置放大器与BPX66型Si-PIN探测器连接,在室温下对241Am源进行测量,其能量分辨率可达到3.03%@59.5 keV。[Background]Traditional charge-sensitive preamplifiers use high-resistance resistors as low-frequency feedback circuit.The thermal noise introduced by high-resistance resistors is the main source of preamplifier noise.[Purpose]This study aims to design and develop a novel charge-sensitive preamplifier by using N-channel junction field effect transistor and RC(Resistor-Capacitance)low-pass network instead of traditional high resistance feedback resistor.[Methods]A junction field-effect transistor and an integrated operational amplifier were used to form an amplifying circuit with advantages of high input impedance and large open-loop gain.A high-pass loop was formed by a small capacitance capacitor to provide a high-frequency feedback loop for the circuit and integrates nuclear pulse current at the same time.The RC low-pass network constituted a DC(direct current)feedback loop to provide a stable DC operating point for the circuit,and a voltage divider for the N-channel junction field effect transistor operating in a forward bias state to realize a feedback capacitor for continuous discharge of its charge.[Results]The charge-sensitive preamplifier was connected with BPX66 Si-PIN detector and the 241Am source was measured at room temperature.The energy resolution of 3.03%@59.5 keV was achieved.[Conclusions]Compared with the traditional resistive capacitance feedback charge-sensitive amplifier,this circuit can effectively over-come the noise introduced by the large-resistance feedback resistor,especially for semiconductor detectors such as Si-PIN.

关 键 词：电荷灵敏前置放大器 半导体探测器 结型场效应管 正向偏置 RC低通网络 

分 类 号：TL821[核科学技术—核技术及应用]