First- and Second-Order Sections
Many active filter structures are based on first- and second-order sections. In this chapter, we will first discuss different types of sections with respect to their transfer functions. Next, we will classify, analyze, and compare different realizations that are based on resistors, capacitors, and with one or several operational amplifiers, transconductors, or current conveyors [58, 130]. These circuits can, of course, be implemented with discrete components, but this is of less interest because a large number of active elements are often needed and the cost and the power consumption becomes high. Integrated active elements are considerably cheaper and consume less power.