纳伏级微弱信号放大电路的设计

摘要

For the actual needs of the field of engineering measuring,designing an amplification circuit of weak signal which is the Nan voltmeter level.Selecting a low noise differential signal amplifier chip to reduce the equivalent input noise.Also designing the corresponding signal conditioning circuit,Using the multi-stage amplifier circuit mode,after a multi-level filtering,multi-level amplifying,gradually increasing the signal to noise ratio.Through the experiment,using the noise of different frequency bands to verify the improvement of the SNR.And using the Multisim Simulation software to analyze the system noises.Effectively inhibit all kinds of noise in the low-frequency bands,and the signal to noise ratio has been improve more higher.%针对工程测量领域的实际需求,设计了纳伏级微弱信号的放大电路,在信号输入端,通过仿真软件仿真设计,最终选用AD公司的超低噪声差分信号放大芯片AD620,放大倍数为10倍,降低了等效输入噪声。设计了相应的信号调理电路,采用多级放大电路组态方式,运用超低噪声四运放（OP470A）来组建多级带通滤波器,经过多级滤波、多级放大,逐步提高信噪比。通过实验,采用不同频段的噪声,验证SNR的改善情况。利用Multisim仿真软件对系统噪声进行了分析,分析结果显示,在低频段有效地抑制对电路造成影响的各种噪声,信噪比得到了较大的提升。