INTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS Int. J. Circ. Theor. Appl. 2008; 36:739–755 Published online 21 September 2007 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/cta.455 LETTER TO THE EDITOR Universal resistorless current-mode filters employing CCCIIs Erkan Yuce 1, ∗, † , Ali Kircay 1 and Sezai Tokat 2 1 Department of Electrical and Electronics Engineering, Pamukkale University, 20070 Kinikli-Denizli, Turkey 2 Department of Computer Engineering, Pamukkale University, 20070 Kinikli-Denizli, Turkey SUMMARY In this paper, four different-type second-order current-mode filters, employing second-generation current- controlled conveyors (CCCIIs) and two capacitors, are proposed. The first two of the presented filters can simultaneously realize high-output impedance low-pass, band-pass and high-pass responses. Also, the two filters can provide notch and all-pass filter responses with interconnection of the relevant output currents. The first developed one needs no critical active and passive element matching conditions and/or cancellation constraints. The second and third introduced ones employ only grounded capacitors. The fourth proposed filter derived from the third one uses only plus-type single output CCCIIs (CCCII + s). The fifth filter can be constructed using commercially available active devices such as AD844s along with additional resistors instead of CCCII + s of the fourth proposed filter to perform experimental test easily. All of the proposed filters have low active and passive element sensitivities. Time and frequency domain analyses are performed for the first, second and third realized filters using SPICE simulation program. Also, experimental test is achieved for the fifth filter. In this study, stability problems attributed to non-ideal gains of the CCCIIs and signal limitations of the first, second and third introduced filters due to restricted power supply voltages are investigated. Copyright 2007 John Wiley & Sons, Ltd. Received 29 March 2006; Revised 6 August 2007; Accepted 14 August 2007 KEY WORDS: current-controlled conveyors; current-mode circuits; analog filters; signal limitations; stability problems 1. INTRODUCTION Much research has been devoted to the realization of current-mode (CM) filters [1–17] employing various active devices because of their versatility and convenience for practical usages in many areas, such as communication systems and signal processing. Thus, a number of CM filter designs are proposed in the literature employing operational amplifiers (OAs) [1], current conveyors (CCs) ∗ Correspondence to: Erkan Yuce, Department of Electrical and Electronics Engineering, Pamukkale University, 20070 Kinikli-Denizli, Turkey. † E-mail: dr erkanyuce@yahoo.com Copyright 2007 John Wiley & Sons, Ltd.