RC有源滤波器的设计

摘要

滤波器是一种能使有用频率信号通过而同时抑制（或衰减）无用频率信号的电子电路或装置。在工程上，常用它来进行信号处理，数据传送或抑制干扰等。以往滤波器主要采用无源元件R、L、和C组成，目前一般用集成运放、R、C组成，常称为有源滤波器。

由RC元件与运算放大器组成的RC有源滤波器，其功能是让一定频率范围内的信号通过，抑制或急剧衰减此频率范围以外的信号。可用在信息处理、数据传输、抑制干扰等方面，但因受运算放大器频带限制，这类滤波器主要用于低频范围。根据对频率范围的选择不同，可分为低通(LPF)、高通(HPF)、带通(BPF)与带阻(BEF)等四种滤波器，

具有理想幅频特性的滤波器是很难实现的，只能用实际的幅频特性去逼近理想的。一般来说，滤波器的幅频特性越好，其相频特性越差，反之亦然。滤波器的阶数越高,幅频特性衰减的速率越快，但RC网络的节数越多，元件参数计算越繁琐，电路调试越困难。任何高阶滤波器均可以用较低的二阶RC有滤波器级联实现。

在一个实际的电子系统中，有时输入信号往往受干扰等原因而含有一些不必要的成分，应当把它衰减到足够小的程度。而在另一些场合，有时我们需要的信号和别的信号混在一起，应当 设法把我们需要的信号挑出来。要解决这些问题都需要采用有源滤波器。

关键词：滤波器 RC 频率 信号

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Abstract

Filter is a frequency signals can be useful while inhibiting (or attenuation) unwanted frequency signals of electronic circuits or devices. In engineering, used it for signal processing, data transfer or suppress interference. The past, the main use of filters and passive components R, L, and C, and currently the general use of integrated operational amplifier, R, C composition, often referred to as active filters.

By the RC components and the composition of op-amp RC active filter, its function is to allow a certain frequency range signals, inhibit or sharp

attenuation outside the scope of this frequency signal. Can be used in information processing, data transmission, interference suppression and so on, but due to limited bandwidth operational amplifier, such filter is mainly used for

low-frequency range. Based on the choice of different frequency range can be divided into low-pass (LPF), high pass (HPF), band-pass (BPF) and band-stop (BEF) and other four kinds of filters.

Amplitude-frequency characteristics with ideal filter is very difficult to achieve, can only use the actual rate to approximate the ideal frequency characteristics. In general, the amplitude frequency characteristics of the filter the better, the worse the phase frequency characteristics, and vice versa. Higher order filters, amplitude-frequency characteristics decay rate was faster, but the RC network, the more sessions, the more complicated calculation of device parameters, circuit debugging more difficult. Any order filters are available with a lower second-order RC filter cascade realization.

In a practical electronic system, sometimes the input signal is often subject to interference and other factors which contain unnecessary ingredients, that it should be small enough degree of attenuation. While in other occasions, and sometimes we need mixed-signal and other signals should be managed to pick out the signal that we need. To solve these problems need to use active filters.

keyword： Filter RC Frequency Signal

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