有源濾波器與開關(guān)電容濾波器的性能比較
摘要： 對模擬信號進(jìn)行濾波，其基本原理就是利用電路的頻率特性實(shí)現(xiàn)對信號中頻率成分的選擇。根據(jù)頻率濾波時(shí)，把信號看成是由不同頻率正弦波疊加而成的模擬信號，通過選擇不同的頻率成分來實(shí)現(xiàn)信號濾波。針對本應(yīng)用所要求的帶通濾波及放大，可以有多種方案，其中使用比較多的是由R、C及集成運(yùn)放組成的有源帶通濾波器和開關(guān)電容濾波器。
Abstract：
Key words :
對模擬信號進(jìn)行濾波，其基本原理就是利用電路的頻率特性實(shí)現(xiàn)對信號中頻率成分的選擇。根據(jù)頻率濾波時(shí)，把信號看成是由不同頻率正弦波疊加而成的模擬信號，通過選擇不同的頻率成分來實(shí)現(xiàn)信號濾波。針對本應(yīng)用所要求的帶通濾波及放大，可以有多種方案，其中使用比較多的是由R、C及集成運(yùn)放組成的有源帶通濾波器和開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器" 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title="開關(guān)電容濾波器">開關(guān)電容濾波器" title="開關(guān)電容濾波器">開關(guān)電容濾波器。
1 帶通濾波器
帶通濾波器的主要性能參數(shù)有：
(1)中心頻率增益K0：輸入為中心頻率信號時(shí)的電壓放大倍數(shù)。
(2)中心頻率f0：它只與濾波用的電阻和電容元件的參數(shù)有關(guān)，是帶通濾波器通帶內(nèi)電壓增益最大點(diǎn)的頻率。
(3)截止頻率fL和fH：輸出幅值為×輸入×中心頻率增益時(shí)所對應(yīng)的頻率，帶通濾波器有兩個(gè)，分別為低頻截止頻率fL和高頻截止頻率fH。
(4)通帶寬度BW：高頻截止頻率fH與低頻截止頻率fL之差。
(5)品質(zhì)因數(shù)Q；對帶通濾波器而言，Q值等于中心頻率f0與通帶寬度BW之比。
2 有源濾波器
有源濾波器是由無源元件(一般用R和C)和有源器件(如集成運(yùn)算放大器)組成。這類濾波器的優(yōu)點(diǎn)是：通帶內(nèi)的信號不僅沒有能量損耗，而且還可以放大，負(fù)載效應(yīng)不明顯，多級相聯(lián)時(shí)相互影響很小，利用級聯(lián)的簡單方法很容易構(gòu)成高階濾波器，并且濾波器的體積小、重量輕、不需要磁屏蔽(由于不使用電感元件)。缺點(diǎn)是：通帶范圍受有源器件(如集成運(yùn)算放大器)的帶寬限制，需要直流電源供電，可靠性不如無源濾波器高，在高壓、高頻、大功率的場合不適用。本實(shí)驗(yàn)采用平常使用比較多的多路負(fù)反饋二階帶通濾波器，如圖1所示。
2．1 有源濾波器參數(shù)設(shè)計(jì)
其傳遞函數(shù)的一般形式為：
式中ω0：帶通濾波器中心角頻率，Q：品質(zhì)因數(shù)，K0：ω=ω0時(shí)帶通濾波器的增益。設(shè)計(jì)中經(jīng)常取C1=C2=C，則：
根據(jù)實(shí)際要求選擇每一級帶通濾波的參數(shù)為：f0=12Hz，GAIN=10，Q=6。然后再根據(jù)具體已有標(biāo)稱的電阻、電容值選擇每一級帶通濾波的器件大?。?R1=17．88K，R2=2．69K，R3=324K，C=0．494μF，經(jīng)計(jì)算得到的理論值為f0=11．71Hz，GAIN=9．06，Q=5．9。
2．2 有源濾波器實(shí)驗(yàn)及數(shù)據(jù)
圖2為測試電路，由該電路得到的實(shí)驗(yàn)數(shù)據(jù)見表1。當(dāng)輸入頻率在中心頻率附近變化時(shí)，輸出信號的相位變化比較明顯。
3 開關(guān)電容濾波器
開關(guān)電容濾波器是一種新型的大規(guī)模集成器件，其主要特點(diǎn)是用開關(guān)和電容來代替電路中的電阻．是數(shù)字電路和模擬電路的結(jié)合，可以將很多有源的RC濾波器轉(zhuǎn)換成開關(guān)電容濾波器。開關(guān)電容濾波器在使用方面的最大優(yōu)點(diǎn)是無需更換元件，只需改變時(shí)鐘頻率和編程引腳電平就可以在一定的范圍內(nèi)改變?yōu)V波器的中心頻率和Q值，這給濾波器的設(shè)計(jì)、使用帶來很大方便。但是開關(guān)電容濾波器具有開關(guān)噪聲和時(shí)鐘噪聲。
3．1 開關(guān)電容濾波器原理
開關(guān)電容的一種結(jié)構(gòu)如圖3所示，起開關(guān)作用的MOS管T1和T2是由時(shí)鐘信號φ和
來控制的，φ和反相的。當(dāng)時(shí)鐘信號φ為高電平時(shí)，T1管導(dǎo)通，T2管截止，電容C與1—1’端接通，充電電荷為Q=CV1；當(dāng)時(shí)鐘信號高電平時(shí)，T2管導(dǎo)通，T1管截止，電容C與2—2’接通，充電電荷為Q=CV2。若設(shè)電路的時(shí)鐘周期為TC，則在此時(shí)間內(nèi)從1一1’端向2—2’端傳輸?shù)碾姾蔀椤鱍=Q1-Q2，由1一1’端流向2—2’端的平均電流為I=△Q／TC=C(V1-V2)／TC。
如果時(shí)鐘頻率fclk=1／TC比信號的頻率高得多，開關(guān)電容相當(dāng)于一個(gè)電阻R，等效電阻值為R=(V1—V2)／I=TC／C=1／fclkC。
顯然，等效電阻的值與時(shí)鐘頻率和電容大小成反比。對于由RC構(gòu)成的濾波器就只需將電阻用開關(guān)電容代替，就可以組成開關(guān)電容濾波器，則電路的時(shí)間常數(shù)τ=RC=C2／fclkC1。
上述表明龜路的頻響特性由時(shí)鐘頻率與電容比值決定，與電容的絕對值無關(guān)。開關(guān)電容濾波器實(shí)質(zhì)上屬于調(diào)制或采樣系統(tǒng)，調(diào)制(采樣)頻率由分頻比決定。
3．2 開關(guān)電容濾波器實(shí)驗(yàn)及數(shù)據(jù)
為了滿足放大倍數(shù)的要求，通過給開關(guān)電容濾波器芯片編程引腳特定的高低電平選擇Q=10.7，中心頻f0=12.14Hz，時(shí)鐘fclk=2.405k Hz，用兩片開關(guān)電容芯片級聯(lián)成四級得到的。圖4所示為一片開關(guān)電容濾波器實(shí)驗(yàn)電路圖。實(shí)驗(yàn)數(shù)據(jù)如表2所列。
4 結(jié)束語
通過對實(shí)驗(yàn)數(shù)據(jù)的分析得出，帶通濾波器中Q值越高則通頻帶越窄，也就是說濾波器對頻率的選擇性就越好，對干擾信號的抑制能力也就越強(qiáng)，但并不是Q值越高電路越好越穩(wěn)定。若Q值取過大，當(dāng)濾波器中心頻率變動時(shí)，有用信號通過濾波器時(shí)將產(chǎn)生較大的相位誤差和幅值誤差。因此在濾波器滿足濾波質(zhì)量前提下，Q值盡可能小。
有源帶通濾波器的無輸入時(shí)輸出噪聲較小，輸出信號幅值較穩(wěn)定，但當(dāng)Q較大時(shí)輸入信號頻率在中心頻率附近變化，輸出信號的相位變化較大。
開關(guān)電容濾波器可以很方便的改變中心頻率和Q值，但是受開關(guān)噪聲和時(shí)鐘噪聲影響，在沒有輸入信號的情況下，輸出有比較大的噪聲信號。
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