Design of a fully differential current mode operational amplifier with improved input-output impedances and its filter applications

Altun M., KUNTMAN H.

AEU-INTERNATIONAL JOURNAL OF ELECTRONICS AND COMMUNICATIONS, vol.62, no.3, pp.239-244, 2008 (SCI-Expanded) identifier identifier


In this paper, a CMOS implementation of a fully differential current-mode operational amplifier (COA) is presented. To achieve very low input resistance, a new technique based on a positive feedback is used in the input transimpedance stage. Additionally, traditional current output stage (Arbel Goldminz output stage) with improved output resistance is selected as a transconductance stage. Results of simulations exhibit 96 dB DC gain, nearly 120 Omega input, 30 M Omega output resistances and a gain-bandwidth product exceeding 90 MHz. The proposed COA is operated under +/- 1.5 V voltage supplies and designed with 0.35-mu m CMOS process. Furthermore, COA-based fourth-order band-pass (BP) filter consisting of Butterworth low-pass (LP) and high-pass (HP) filters is realized as an application example. SPICE simulation results are included to verify correctness of the designs. (c) 2007 Elsevier GmbH. All rights reserved.