离子迁移谱电信号前置放大电路的设计与仿真

Design and Simulation of Pre-amplification Circuit for IMS Current Signals

离子迁移谱产生的电流信号幅度为pA级,往往淹没在强噪声中难以用常规的仪器测量出来,为了检测如此微弱的电流信号,前置级放大电路是最关键的环节,其设计优劣直接关系到信号数据采集系统的精度。本文采用锁定放大技术的原理,根据OPA128芯片的特点,提出了信号检测的方法和前置放大电路的设计。经过Multisim10软件仿真,该电路检测pA级微电流,误差不超过4.4%,在测量范围内有较好的线性度,满足检测离子迁移谱微电流的要求。该电路也对低频微弱电信号以及直流信号的放大都具有一定的参考价值。

The current signals produced by IMS locate at pA level, which is often difficult to be detected in strong noise by normal apparatuses. In order to examine the weak current signals, the preamplification circuit is the most important link. The design is related to the precision of signal detection system directly. In this paper, a signal detection method and a pre-amplifier circuit design are elaborated according to the Lock-in amplifier （LIA） principle and OPAl28 chip characteristic. The Muhisim10 simulation results indicate that the error of pA level current is below 4.4% and the circuit has good performance in linearity in measurement range, which achieves the IMS current detection demand. This circuit can be also used for amplifying direct current and low frequency weak current signal.