基于交流调制技术的弱电流放大器研制

在射线强度测量中，积分电离室输出的电流信号在10–10~10–15 A范围内，该弱电流信号需要转换和放大才可以进行采集。针对积分电离室本文设计了一种弱电流信号放大系统，采用交流调制技术将待测弱直流电流信号调制为交流电压信号，再经放大、相敏检波、滤波等电路处理后得到直流电压信号，最后进行数据采集；同时在系统中引入直流负反馈后缩短了电流测量的响应时间。采用标准电流源测试了系统输入输出线性及响应特性，测试了积分电离室检测氚靶的β射线。测试结果表明:该系统能够有效放大10–14~10–11 A范围内的弱电流信号且有较好的线性和响应时间特性，电流测量灵敏度达到了10–14 A，该系统具有良好的工程应用前景。

Development of a Weak Current Amplifier Based on AC Modulation Technology

In the measurement of ray intensity, the current signal from the integral ionization chamber is in the range of 10-10~10-15 A, which needs to be converted and amplified before it can be collected. A weak current signal amplification system is designed for the integral ionization chamber in this paper, using AC modulation technology to modulate the weak DC current signal to be measured into AC voltage signal, and then obtains the DC voltage signal after amplification, phase-sensitive detection, filtering and other circuit processing, and finally the data is collected. At the same time, the DC negative feedback is introduced into the system to shorten the response time of current measurement. The linear and response characteristics of the system were tested by the standard current source, and the β ray of tritium target was detected by an integral ionization chamber. The test results show that the system can effectively amplify the weak current signal in the range of 10-14~10-11 A with good linearity and response time characteristics, and the current measurement sensitivity is 10-14 A, the system has a good prospect of engineering application.