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设计了一种用于核磁共振测井仪的低噪声模拟接收电路。第1级放大为自主构建的仪器用放大器,其增益为52dB,选用最佳源电阻与天线谐振阻抗相近的超低噪声宽带运放LMH6626保证电路的低噪声性能。对第1级放大器的噪声性能进行了理论分析,其噪声系数为1.45。实验测试结果表明,电路最大增益为112dB,频率范围为400kHz～1MHz,可对核磁共振信号进行低噪声放大,并已成功应用于核磁共振测井仪实验室样机中。
A low-noise analog receiver circuit designed for nuclear magnetic resonance logging tool was designed. The first stage of amplification for the independent construction of the instrument amplifier, the gain of 52dB, use the best source resistance and antenna resonant impedance similar to the ultra-low-noise broadband operational amplifier LMH6626 circuit to ensure low noise performance. The noise performance of the first stage amplifier is theoretically analyzed with a noise figure of 1.45. Experimental results show that the maximum gain of the circuit is 112dB and the frequency range is 400kHz ~ 1MHz. It can amplify the nuclear magnetic resonance signal with low noise and has been successfully applied in the laboratory prototype of the nuclear magnetic resonance logging tool.