All-pass filters using DDCC- and MOSFET-based electronic resistor

The main motivation in this paper is to draw attention to the tunability and input-signal amplitude limitations when a nonlinear device is used as a resistor. For this purpose, two first-order all-pass filters are proposed using differential difference current conveyor (DDCC), a capacitor and a resistor without element-matching restriction. These all-pass filter circuits can be made electronically tunable with electronic resistors. Tunability and input-signal amplitude limitations of the proposed circuits due to the operational restrictions of the electronic resistors are examined. PSPICE simulations confirm the validity and the practical utility of the proposed circuits. Copyright (C) 2010 John Wiley & Sons, Ltd.