Nuclear Techniques ›› 2019, Vol. 42 ›› Issue (9): 90402-090402.doi: 10.11889/j.0253-3219.2019.hjs.42.090402


Design of charge sensitive preamplifier based on RC low pass feedback

Yi ZENG Guoqiang GE Liangquan HU Chuanhao HE Li HOU Yang LI Xinchi RONG   

  1. Applied Nuclear Technology in Geosciences Key Laboratory of Sichuan Province, Chengdu University of Technology, Chengdu 610059, China
  • Received:2019-05-27 Revised:2019-07-11 Online:2019-09-10 Published:2019-09-18
  • Supported by:
    National Key R&D Projects of China(2017YFC0602100);National Natural Science Foundation of China(41474159)

Abstract: 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.


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.


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.


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.


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.

Key words: Charge-sensitive preamplifier, Semiconductor detector, Junction field effect transistor, Forward bias, RC low-pass network

CLC Number: 

  • TL821