在产品的研制过程中发现一种由独石电容构成的有源滤波器发生了谐波失真,并且随着输入信号电压的增大,谐波失真增强,更换电容后谐波失真消失,进而确定是独石电容对滤波器产生了影响.独石电容按材质分为NPO、X7R、Y5V三种类型,对不同材质的独石电容分别进行了实验,得到了不同材质的独石电容的电压-电容特性.首次给出了电容随电压变化的曲线,并将此特性应用于滤波器转移函数中进行分析、仿真,仿真结果与实验结果相吻合.最后通过对实验结果进行总结,给出了滤波器设计中电容的选择标准.%One kind of active filter composed by multi-layer ceramic capacitor causing harmonic distortion is found in the product making process, and the harmonic distortion increases with the input signal voltage increases. When replaced the multi-layer ceramic capacitor, the harmonic distortion disappear, then make sure that the multi-layer ceramic capacitor affects the filter. The multi-layer ceramic capacitor has three types according to the material, including NPO, X7R and Y5V. Then the multi-layer ceramic capacitor of different materials are tested, and the voltage-capacitance characteristics of different materials multi-layer ceramic capacitor are gotten. For the first time, the curve of voltage-capacitance is given. Simulation is consistent with the experimental results when the voltage-capacitance characteristics attribute to filter transfer function for analysis and simulation. Finally, summary is done through experiments, then the selection criterion of the capacitors in the filter design is given.
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