瞬变电磁低噪声前置放大器研制

Research on low noise preamplifier of transient electromagnetic instrument

为了增大瞬变电磁勘探深度,充分利用晚期道数据,针对瞬变信号频带宽等特点和低噪声运放放大电路的设计原则,通过对放大电路的噪声来源和降低噪声措施的研究,设计了基于超低噪声运算放大芯片LT1028的低噪声差分前置放大电路.建立模型对噪声进行计算和仿真,得出的单运放噪声和总噪声分别为3.2uVrms和4.53uVrms.对实际电路进行噪声测试,得到的噪声频谱图表明在0～100kHz的频率范围内,电路噪声在10～20uVrms之间,设计的差分前置放大电路具有很低的噪声水平,能够满足瞬变信号前置放大的需要.

ransient electromagnetic method is widely used in many fields such as mineral exploration,groundwater exploration and engineering survey.In order to increase the transient electromagnetic exploration depth,making full use of the advanced way data,we design a low noise and differential preamplifier circuit,and also analyze its noise,based on the principles of low noise amplifier circuit designing,and the characteristics of TEM signal of wide frequency band,dynamic range,and huge differences between late and early signals in amplitude and decay rate.Two low noise amplifiers LT1028 are used in this design to reduce the circuit noise.The simulation results and the theoretical calculation results of the noise are completely consistent.And the circuit noise spectrum chart we get by measuring indicates that the circuit we designed has a low noise level,which can satisfy the needs of transient signal preamplifier.