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分析了无输入变压器单通道斩波式直流放大器的噪声和漂移,得出了等效输入噪声和等效输入误差电压公式,给出了一种低噪声直流放大器方案,并讨论了放大器的稳定性。实验表明,该放大器可克服一般输入变压器耦合式高灵敏度放大器体积大,成本高,输入阻抗低,被测信号源不能浮地等缺点;信号源内阻小于1kΩ时,灵敏度高于0.1μV,时间漂移小于1μV/7h,响应时间小于5s。
The noise and drift of a single-channel chopper-type DC amplifier without input transformer are analyzed. The equivalent input noise and equivalent input error voltage formula are obtained. A scheme of low-noise DC amplifier is given and the stability of the amplifier is discussed . Experiments show that the amplifier can overcome the shortcomings of the general input transformer-coupled high-sensitivity amplifier, such as large volume, high cost, low input impedance, and undetected signal source. When the internal resistance of the signal source is less than 1 kΩ, the sensitivity is higher than 0.1 μV and the time drift Less than 1μV / 7h, the response time is less than 5s.