一种具有偏置电流温度补偿的弱信号放大电路

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对于工作在宽温度范围为25~175℃的核磁共振测井仪器微弱信号放大电路,随温度变化的偏置电流作用在不对称的差分信号源内阻上会对放大电路产生不同程度的干扰。基于低热阻封装的ADA4898-2低噪声运算放大器,设计一种带偏置电流温度补偿的微弱电压信号放大电路,其增益设计值85.8dB。理论分析和实验室测试均表明,在输入信号电压幅度最小为百nV、频率范围为400kHz~1MHz时,偏置电流温度补偿电路有效地降低了偏置电流引入的干扰,且不引入新的噪声源,在宽温度范围为25~175℃下有良好的线性度和频率响应。

Aiming at the weak voltage signal amplification circuit of nuclear magnetic resonance logging tool working at a wide range of temperatures(25~175 ℃),bias current varying with temperature can affect the amplifier to different degrees when effect the dissymmetrical differential signal source resistance.Based on low noise operational,low thermal resistance package am plifier ADA4898-2,a voltage signal amplification circuit with bias current temperature compensation was designed.Its gain is 85. 5 dB.Theoretical analysis and experimental data show that bias current temperature compensation circuit effectively reduces the interference caused by the bias current when the input signal s amplitude is hundreds of nanovolt,and frequency range 400 kHz to 1000 kHz.Furthermore,it won t increase the noise.At wide range of temperatures(25~175 ℃)environment,its linearity and fre quency response is well.