Low-power high-order band-pass active-RC allpole filters using a "lossy" LP-BP transformation

The design procedure for high-order single amplifier BP filters is presented. A method for the design of 2(nd)- and 4(th)-order band-pass (BP) active-RC filters using a modified low-pass to band-pass (LPBP) frequency transformation, was already presented in previous works [1],[2]. It was shown that a BP filter could be realized simply by the substitution of resistors and capacitors of the ladder in a low-pass (LP) prototype filter, by serial and parallel RC circuits. Such a substitution results from a so-called, "lossy" LP-BP transformation. In this paper, the design procedure is extended to higher-order BP filters, such as 6(th)- and 8(th)- order. The design procedure is simple, and the closed-form design equations, are presented. Furthermore, it is shown that "impedance tapering" decreases sensitivities to component tolerances for the LP prototype, as well as for the resulting BP filter. The Schoefer's sensitivity measure is used for the sensitivity analysis.