摘要
滤波器的基本功能是从输入信号中选出所需要的频率成分,而把其它不需要的频率成份滤除掉，有源滤波器广泛用于通信和测量电路中，特别适用于工作在低频和超低频波段,最低频率可延伸到1HZ 以下。
有源滤波器的设计先根据信号处理的要求得到一个实有理近似传递函数H( S)，根据传递函数进行电路实现一般有两种类型，即直接型和级链型， 直接型将H ( s) 作为一个整体来直接实现,级链型将H( s) 分解为一阶和二阶基本节函数来级链实现，在级链实现中，传递函数用若干个二阶级或一阶级滤波器的级链来实现，
有源滤波器从带通性能看可分成低通滤波器(L PF)，高通滤波器(HPF)，带通滤波器(BPF) 和带阻滤波器(BEF) 等。利用计算机计算和绘制出大量优化图表，查索图表就可以迅速得到滤波器的元件参数和各种特性，设计出所要求的滤波器。
关键词：有源滤波器，截止频率，传递函数
Abstract
Filter's basic function is selects the frequency component needed which from the input signal,The other frequency components which is not needed is filtered out, APF is widely used in communications and measurement circuit, Particularly applicable to work in low-frequency and ultra-low-frequency band, the lowest frequency may extend to 1HZ below
The active filter's design obtains on signal processing requirements are a function H(s).According to a transfer function circuits are generally two types, a direct and chain type. Direct-to H (s) as a whole to realize direct, Another divided the H (s) into first and second order of a basic, In the level chain realizes, The transfer function realizes with several two social classes or a social class filter's level chain,
Active from the band-pass filter performance can be divided into low-pass filter (L PF), high-pass filter (HPF), Band-pass filter (BPF) and the band Filter (BEF), and so on,Using computer calculations and drawing a lot of optimization of charts, Check on the chart can quickly filter components of various parameters and characteristics, Designed to filter,
Keywords: APF, Cut-off frequency, Transfer Function
