用于感应式磁传感器低噪声前置放大器的研制

摘要

感应式磁传感器是频率域电磁法（ FEM）中使用最广泛的磁传感器，通常由感应线圈和前置放大器组成，其中前置放大电路是影响磁感应式磁传感器性能指标的核心因素。为了增加感应式磁传感器探测深度和微弱磁场信号的能力，要求前置放大电路具有宽频带和低噪声等性能。基于磁通负反馈的原理设计并研制了斩波前置放大器，有效抑制了感应线圈的输出噪声，使感应线圈谐振频率两侧具有平坦的幅频特性曲线，拓宽了感应式传感器的响应频带。在屏蔽室内对斩波前置放大器的性能指标进行了测试，其频带范围为0.001Hz～10 kHz，输入噪声为3.75 nV／ Hz ，为感应式磁传感器在实际中的应用提供了性能保障。%Inductive magnetic sensor is one of the most widely utilized magnetic sensors in frequency domain electromagnetic method (FEM).Generally,inductive magnetic sensor consists of inductive coil and preamplifier which is the critical factor to affect the performance of inductive magnetic sensor .In order to make inductive magnetic sensor detect weak magnetic signals and improve the detection depth ,the preamplifier with broadband and low noise is required .The chopper preamplifier was designed and devel-oped which was based on the principle of magnetic flux negative feedback .As a result,the output noise of the induction coil is in-hibited effectively and the both sides of the resonant frequency of induction coil have a flat amplitude -frequency curve which can broaden the inductive sensor response band .The performance of chopper preamplifier was tested in shielded room .The frequency range is from 0.001 Hz to 10 kHz,and the input noise is 3.75nV/√Hz,which guarantees performance for inductive magnetic sen-sor in real application .