Active RC filters were first applied in the late 1950s. Since then, there has been a rapid development in both theoretical research and practical realization methods, as witnessed by the appearance of some 3,000 publications on active RC filters. This abundance of literature has, however, caused a great deal of confusion for non-specialist engineers. In order to solve a problem of filter design, a prolonged study is usually needed in order to make the correct choice between a wide variety of filter structures. Furthermore, most publications are intended to solve detailed problems for experts...