TABLE OF CONTENTS Active filters provide compact, lightweight signal-processing components for a wide variety of applications, such as voice and video signal processing for the communications industry, telemetry, biomedical electronics, radar, sonar, and seismic analysis, to name a few. Much of the motivation for considering active filters stems from the progress that has occurred in integrated-circuit technology. Such developments as the monolithic operational amplifier and the thick- and thin-film technologies enable one to realize high-quality, miniature, hybrid integrated-circuit active- RC filters at low cost. These filters are usually designed in the frequency range under 20 kHz, with much of the volume applications at voice frequencies [i.e., 4 kHz and below, e.g., D4-channel bank active- RC filters (see Fig. 1-45)]. For active filters, the upper frequency limit is imposed primarily by the cutoff frequency, or the unity gain-bandwidth product, of available op amps. Active- R and active- C filters, which derive their frequency dependence from the one-pole roll-off of the op amp, serve as alternative means for implementation of active-filters. For this class of filters, the upper limit in Q, and the center frequency is also determined by the stability conditions imposed by the phase response characteristic of the op amp and dynamic range limitations which stem from the noise levels and slew rates (Appendix C) of practical op amps.
This chapter and Chapter 5 are devoted to the analysis, design, and performance of continuous-time active filters. This includes traditional active- RC-type filters and, for high-frequency...
