井下地层流体NMR分析仪微弱信号放大电路设计  

Design of Weak Signal Amplifying Circuit for NMR Analyzer of Downhole Formation Fluid

作　　者：黄琳[1] 龚治宇 孟祥隆 吴磊[3] 

机构地区：[1]中海油田服务股份有限公司测井技术研究院,北京101149 [2]华中科技大学自动化学院,湖北武汉430074 [3]北京理工大学化工与环境学院,北京100081

出　　处：《仪表技术与传感器》2017年第2期27-30,共4页Instrument Technique and Sensor

基　　金：高等学校博士学科点专项科研基金(20130142120065)

摘　　要：针对井下地层流体核磁共振分析仪器回波信号的频率高、强度弱、信噪比低的特性,以及测井仪器工作环境的特殊性,设计了一种低噪声的微弱信号放大电路。电路以低噪声双极性晶体管MAT02为核心的负反馈放大电路作为第一级放大,采用低噪声集成运放AD8130作为第二、三级放大,改善了微弱信号放大电路的噪声性能。实验表明:该电路对于频带4~5 MHz微弱信号,增益可达70 d B,且其等效输入噪声电压为槡2.1 n V/Hz,同时在环境温度0~150℃时有良好的线性度、较平坦的带宽和优良的低噪声性能,可为测井仪器中较高频率的微弱信号测量研究提供参考。Aiming at the characteristics of high frequency,low intensity,low SNR of the underground formation fluid nuclear magnetic resonance（NMR） analysis instrument echo signal and the particularity of the logging instrument working environment,low noise weak signal amplification circuit was designed.Negative feedback amplifying circuit with low noise bipolar transistor MAT02 as core was the first level amplification.And the low noise integrated operational amplifier AD8130 was used as the second and third level amplification,so as to improve the noise performance of the preamplifier.Experimental results show that the frequency band is 4 - 5 MHz,receiving circuit gain is 70 d B,and its equivalent input noise voltage is 2.1 nV/Hz.which has good linearity,relatively flat bandwidth and excellent low noise performance at the environmental temperature of 0 - 150 ℃,providing a reference for the logging instrument in high frequency weak signal measurement study.

关 键 词：核磁测井仪器 微弱信号放大电路 低噪声双极性晶体管 噪声匹配 

分 类 号：TE242[石油与天然气工程—油气井工程]