说明：  滤波器（filter），是一种用来消除干扰杂讯的器件，将输入或输出经过过滤而得到纯净的直流电。对特定频率的频点或该频点以外的频率进行有效滤除的电路，就是滤波器，其功能就是得到一个特定频率或消除一个特定频率。
(Filter (filter), is a device used to eliminate noise interference, the input or output through the filter and get pure DC. The frequency of a particular frequency or frequencies outside the frequency of effective filter circuit is the filter, its function is to get a specific frequency or eliminate a specific frequency.)