Introduction to the Theory and Design of Active Filters

Description

The book, written by two experts in the active network field, is a text as well as a convenient summary of methods used for construction of active filters. Sufficient basic information is available for those wishing to start a new field. On the other hand, detailed information is given on the various performance imperfections caused by nonideal properties of active components. Parts of the text will be useful for undergraduate courses. As a whole, the book is probably more suitable for initial graduate courses, and is also suitable for those who do not wish to search the literature for more detailed information. In an attempt to provide as much basic information as possible, the first two chapters start with filter approximation theory. A number of tables are included to help the reader wishing to construct filters, but the book does not attempt to give detailed information about the approximation problem or to build up deeper knowledge of the field. Chapter 3 is also introductory, dealing with sensitivities of variouskinds. The first sections are sufficiently clear fur any reader. Relevance of the sections on multiparameter statistical sensitivity and the adjoint network concept might be difficult for uninitiated readers.Simple second-order active building blocks are the subject of the fourth chapter. Both ideal and finte-gain, finite-bandwidth amplifers are considered. A similar description of filter sections, which can realize transfer zeros, is given in Chapter 5; it starts with single amplifier building blocks and continues with multiple-amplifiir blocks. Considerable attention is paid to the integrators, their various imperfections and to appropriate compensations. The chapter goes quite deep into the problems caused by amplifier imperfections, and stresses the importance of minimizing sensitivities of network functions with respect to amplifier properties. Modem active filters are usually built as simulations of LC filters, because sensitivities to element changes can be kept low. Chapter 6 is devoted to possible ways of realizing such filters. The generalized immittance converter, the basis of many such networks, is first analyzed in detail and its application to simulation of inductors or to realization of frequency dependent negative resistors is discussed. This material is followed by a description of leapfrog filters and of some more advanced realization possibilities. Again, a considerable amount of practical detail is given in this chapter. The book is concluded by a chapter which discusses problems encountered at higher frequencies and introduces the concept of active networks in which resistances are simulated by switched capacitors. The reader will appreciate the many small and larger examples which accompany every point discussed. The book is easy to read and represents an upto-date summary of active network methods.