%0 Journal Article
%T Low-Voltage Complex Filters Using Current Feedback Operational Amplifiers
%A Panagiotis Samiotis
%A Costas Psychalinos
%J ISRN Electronics
%D 2013
%R 10.1155/2013/915758
%X A novel complex filter topology realized using current feedback operational amplifiers as active elements is introduced in this paper. Offered benefits are the low-voltage operation capability and the requirement for employing only grounded passive elements. Two application examples are provided, where the frequency behavior of the derived filters fulfills the ZigBee and Bluetooth standards, respectively. Their performance evaluation has been done through simulation results at postlayout level, using MOS transistor models provided by AMS C35B4 CMOS process. 1. Introduction Low-IF transceiver architectures suffer from the presence of image signals, caused by the downconversion operation realized by the complex mixing. Unfortunately, due to their symmetrical response around the dc, the conventional real filters do not have the capability for removing the image signals. In order to overcome this problem, a new class of filters denoted by complex filters has been introduced in the literature. Complex filters are constructed from two-path networks, where a pair of signals with equal amplitudes and quadrature phases ( and channels) is applied at their inputs. The concept of complex signal processing is formally described in [1每3]. A significant research effort has been already performed in the literature for designing complex filters suitable for low-IF receivers. The discrete-time topologies in [4, 5] have been derived using the switched capacitor and switched current techniques, respectively. Continuous-time filters have been introduced in [6每21]. The topologies in [6, 7] are companding filters realized by utilizing bipolar transistors. The concept of conventional linear continuous-time filtering and MOS transistors has been used in [8每21]. The topologies in [8每14] offer the capability for resistorless realization and this originated from the employment of the operational transconductance Amplifiers (OTAs) [8每12] or current mirrors (CMs) [13, 14] as active elements. Second generation current conveyors (CCIIs) in single form [15, 16] or fully differential form [17] have been utilized for realizing current-mode complex filters. CCIIs configured as current followers (CFs) and voltage followers (VFs) have been employed in [18], while CCIIs as VFs have been used in [19]. In the topology in [20] operational amplifiers (op-amps) have been used as active elements, while in [21] a number of voltage-mode and current-mode realizations based on transconductance, transresistance, and current amplifiers have been presented and evaluated. Current feedback operational
%U http://www.hindawi.com/journals/isrn.electronics/2013/915758/