一种大电容测量中模拟小信号放大电路的设计

Design of weak signal amplifying circuit in the measurement of large capacitance

在大电容测量中,对大电容上的取样电压信号进行放大处理是最为关键的环节,其设计的优劣直接关系影响到测量系统的准确度。在对现有微弱信号放大器研究的基础上,设计出一种小信号放大电路,该放大电路以高精度的仪器仪表放大器AD623为核心器件,可根据输入电压信号的大小选择不同的增益,实现了1mV～1V范围内电压信号的精确放大,同时该放大器还具有抑制共模干扰、抑制温漂、稳定性好、抗干扰能力强的优点。对该电路做了详细的理论分析和实验论证,实验结果表明该放大器完全可以满足大电容测量的需要,在电子测量领域具有较高的实用价值。

In the measurement of large capacitance, the voltage signal amplification of capacitance is the most important and key link. Whether the design is excellent or inferior is related to test system directly. On the basis of weak signal amplifier which is studied, a kind of is amplifying circuit is designed. This amplifying circuit based on high accuracy instrumentation amplifier AD623 can adjust gain according to the change of voltage signal, and can amplify voltage signal accurately in 1 mV-- 1 V range, has the advantage of suppression of common-mode interference, inhibition of temperature drift,good stability,and strong anti-interference. The paper has detailed theoretic and experimental results to prove this circuit, the experiment shows that the amplifier can meet the requirements of large capacitance measurement and it has highly practical application value in the field of electronic measurement.