New CFOA-based first-order all-pass filters and their applications

Abstract

In this paper, new two first-order all-pass filters (APFs) employing current feedback operational amplifiers (CFOAs) are proposed. The first proposed APF uses two CFOAs while the second one contains three CFOAs. The main features of the both of the proposed APFs are the use of a grounded capacitor, having adjustable gain and possessing low output impedance. Also, the second-proposed APF derived from the first one has high input impedance, and can simultaneously provide both inverting and non-inverting APF responses; nonetheless, both of the proposed APFs need a single passive element matching condition for proper operation. Single phase and multiphase oscillators are included to illustrate applications of the proposed APFs. Several simulations and experiments based on commercially active devices such as AD844s are carried out to verify the theory. © 2019 Elsevier GmbH