采用标称值电容的有源低通滤波器三阶基本节设计

A Design Method for the Third-Order Basic Unit of Low-Pass Active Filters with Capacity Cells of Nominal Values

高阶(n>3)有源滤波器通常由基本节(n≤3)级联而成.在工程实际中,制作基本节时人们都希望选用标称值电容元件的实用设计方法,以使电路中所有电容器的参数均具标称值.对二阶基本节的设计可采用选择标称值电容器的方法,但较少见到三阶基本节的设计有类似方法.本文根据滤波器设计的“系数配比法”,以多路反馈型低通滤波器为例,导出了有源滤波器的单运放三阶基本节采用标称值电容元件的一种设计方法,给出了实用设计程序.1 电路及其传递函数电路如图1所示.其传递函数为:

It is generally hoped that all capacity cells be of nominal values when designing an active filter. Unfortunately, not many such design methods for the third-order basic unit in practice have been reported. With the low-pass active filter with multi-way feedback as an example, a design method for this purpose is proposed and the effectiveness of the parameter calculation is discussed. A practical design procedure is recommended.