Continuous-Time Active Filter Design / Конструкция активного фильтра непрерывного действия

“In this digital age, who needs continuous-time filters?” Such an obvious question, and one which deserves an immediate response. True, we do live in a digital age—digital computers, digital communications, digital broadcasting. But, much though digital technology may bring us advantages over analog systems, at the end of the day a digital system must interface with the real world—the analog world. For example, to gain the advantages that digital signal processing can offer, that processing must take place on bandlimited signals, if unwanted aliasing effects are not to be introduced. After the processing, the signals are returned to the real analog world after passing through a reconstruction filter. Both bandlimiting and reconstruction filters are analog filters, operating in continuous time . This is but one example—but any system that interfaces with the real world will find use for continuous-time filters. <...>