All-pass sections with rich cascadability and IC realization suitability

In this paper, two new circuit configurations for realizing voltage-mode (VM) all-pass sections (APSs) are presented. The proposed circuits employ only two differential voltage current conveyors (DVCCs) and are cascadable with other VM circuits due to their high-input and low-output impedances. The first configuration uses a grounded resistor and a grounded capacitor without requiring matching constraints, whereas the second employs two grounded resistors and a grounded capacitor with a single matching condition. While the first configuration can realize only one all-pass response, the second can provide inverting and non-inverting all-pass responses with selection of appropriate input port. Adding two grounded resistors to the proposed filters, variable gain APSs can also be obtained. As applications, two quadrature oscillators, each of which using one of the proposed all-pass circuits, one grounded resistor and one grounded capacitor are presented. SPICE simulation results are included to verify the theory. Copyright (c) 2010 John Wiley & Sons, Ltd.