10^(-4) V级微弱脉冲信号放大电路设计研究

Design and research of 10^(-4) V level weak pulse signal amplification circuit

微弱脉冲信号(10^(-4) V数量级)一般需要经过信号放大才能用于后端电路处理,设计了一种可用于微弱脉冲信号的放大电路。整个电路主要由电压放大部分和功率放大部分串联构成。其中电压放大是由电荷灵敏放大和二级负反馈串联构成的,而为提高负载能力而设计的功率放大是在射级跟随器的基础上进行改进的.依靠两个特性相同的NPN和PNP三级管以及两个特性相同的二极管构成了推挽型跟随电路,这种设计可消除"开关失真",为消除高压电源带来的电磁干扰,还对电路进行了电磁屏蔽设计。经PCB制备及电路测试,电压信号幅值由10^(-4) V数量级放大到了2V(10~0数量级),放大倍数达到了10 000倍以上,电路总输出端的噪声幅值约为50mV,信噪比为2 000/50=40,可有效分辨有用信号。所设计电路具有放大倍数高、高信噪比、负载能力强、抗干扰等优点,可为微弱脉冲信号的放大电路研制提供参考。

The weak pulse signal (order of 10^-4 V) can be used in the back-end circuit processing generally after signal amplification. This paper aims to design an amplifier circuit that can be used for weak pulse signal. The whole circuit is mainly composed of voltage amplifier and power amplifier in series. Voltage amplification is composed of charge sensitive amplification and two-level negative feedback in series. The power amplification designed to improve the load capacity is modified on the basis of the emitter follower. Relying on two NPN and PNP tertiary tubes with the same characteristics and two diodes with the same characteristics, the push-pull follower circuit is formed. This design can eliminate the “switch distortion”. Electromagnetic shielding design was also designed in the circuit to eliminate the electromagnetic interference caused by the high voltage power supply. After PCB preparation and circuit test, the voltage signal amplitude was amplified from 10 4 V order of magnitude to 2 V (10° order of magnitude), and the amplification factor was over 10 000 times. The noise amplitude at the total output end of the circuit was about 50 mV, and the signal-to-noise ratio was 2 000/50 = 40, which can effectively identify the useful signals. The circuit designed in this paper is characterized by the high amplification factor, high signal-to-noise ratio, strong load capacity and anti-interference, which can provide reference for the development of amplifying circuit of weak pulse signal.