一种基于拓展摆幅的超低噪音微电流检测互阻放大器  

A Kind of Super Low-noise and Microcurrent Detection Transimpedance Amplifier Based on Expanding Swing

作　　者：南瑞亭[1] 刘灼华[1] 

机构地区：[1]广州市交通技师学院,广州510170

出　　处：《日用电器》2017年第2期47-49,54,共4页ELECTRICAL APPLIANCES

摘　　要：精确测量飞安级别的微弱电流需要超低偏置电流的前置放大器。通常,这一类该放大器的输出摆幅相对较低,因此限制了反馈电阻值的提高并最终使得噪声偏大。本研究提出了一种改良版的低噪声互阻放大器,该放大器内部采用大环反馈回路拓展了摆幅,从而允许使用高值电阻达到降低噪声的效果。本研究讨论了该装置的噪声理论、工作原理和电路设计,实现了一个量程为20 V/200 PA的放大器原型。测试结果显示,输出电压摆幅拓展至±20 V以上,直流失调电流约仅有2.5 fA,而白噪声电流低至0.5 fA/√Hz的水平。Accurate measuring of microcurrents in fA range requires an ultra-low bias amplifier which has relative low output swing, limits the value of feedback resistor, and ultimately results a poor noise performances. In this paper, an improved low-noise transimpedance amplifier with a large feedback loop is proposed, so that high-value resistor can be employed to achieve low noise performance. The noise theory, operational principle and circuit imple- mentation are discussed. The prototype is designed with measurement range of 20 V/200 pA, the test results indicates a low white noise level of 0.5 fA/∨ Hz, and an offset bias of -2.5 fA, while providing an output voltage swing expand to above ± 20 V.

关 键 词：微电流 低噪音放大器 输出摆幅 

分 类 号：TM933.1[电气工程—电力电子与电力传动]