Low-sensitivity SAB band-pass active-RC filter using impedance tapering

Abstract

The design procedure of low-sensitivity second-and third-order class-4 Sallen and Key active resistance-capacitance (RC) allpole filters, using impedance tapering, has already been published. There a ladder structure in the positive feedback loop of an operational amplifier was used. In this paper desensitization using impedance tapering is applied to class-3 circuits with negative feedback referred to as a "single-amplifier biquad" (SAB). The RC-section in the negative feedback loop is impedance scaled upwards, from the driving source to the negative amplifier input. Second-order band-pass filters are considered. The improvement comes free of charge; component count and topology remain unchanged, whereas the component values, selected for impedance tapering, account for the significant decrease in sensitivity to component tolerances.

Low-Sensitivity Active-RC Allpole Filters Using Optimized Biquads

“…The complementary transformation provides that all complementary circuits possess identical transfer functions with the same coefficients but with β andβ interchanged (compare coefficients in Tables 1 and 3). This provides the same sensitivity characteristics and the same design strategies for complementary pairs [2]. For example, for both (+) BP-Type B filer in Figure 2 For every circuit in Figure 3, the optimum design procedures are summarized in Table 4.…”

“…Preliminary results of the new design method have been presented elsewhere [1][2][3][4][5] for filters of second-and thirdorder and for low-pass (LP), band-pass (BP) and high-pass (HP) filter types. For those filters, sensitivity to component tolerance, which is considered one of the main performance criteria, was investigated in detail.…”

Optimized Second- and Fourth- Order LP and BP Filters

“…A design procedure of low sensitivity second-order lowpass (LP) and band-pass (BP) filters is presented in [1][2][3][4][5][6].…”