2. Analog Filters

‘Filter’ is a general term. It is used to separate desired parts from unwanted parts of an original set. In an electrical point of view filters have a variety of duties. Filters are used to cut a particular range of the frequency spectrum of an electrical quantity out of the overall frequency spectrum to retrieve the interesting information out of the plenty of information channels and noise. They can be used as equalizers or matched filter in transmission channels in order to compensate distortions caused by the transmission channel itself. Filters can also be employed for smoothing purposes at the output of digital-to-analog converters. This chapter deals with the characterization of filters, it gives an overview of some analog filters and describes the Butterworth-filter approach in more detail.