The Seventh PSU Engineering Conference 21-22 May 2009 CC-CCTA-Based Current-mode Quadrature Oscillator Nitiphat Pisutthipong 1 Phamorn Silapan 2 Montree Siripruchyanun 3 1 Department of Electronics, Faculty of Industrial Education, Rajamangala University of Technology Isan Khonkaen Campus, Khonkaen, 30000 2 Electric and Industrial Program, Faculty of Industrial Technology, Uttaradit Rajabhat University, Uttaradit, 53000 3 Department of Teacher Training in Electrical Engineering, Faculty of Technical Education, King Mongkut’s University of Technology North Bangkok, Bangkok, 10800 E-mail: jibpepis@hotmail.com 1 , phamorn@mail.uru.ac.th 2 , mts@kmutnb.ac.th 3 Abstract This article presents a current-mode quadrature oscillator using current controlled current conveyor transconductance amplifiers (CC-CCTAs) as active elements. The proposed circuit is realized from a lossy integrator and a lossy differentiator. The oscillation condition and oscillation frequency can be electronically controlled via input bias currents. The proposed oscillator can be applied to provide AM/ASK signals with the above major advantages. The circuit description is very simple, consisting of merely 2 CC-CCTAs and 2 grounded capacitors. By absent of any external resistors and using a few number of external passive components, the proposed circuit is then suitable for IC architecture. The proposed circuit, due to high output impedances, enabling easy cascading in current-mode signal processing. The PSPICE simulation results are depicted, and the given results agree well with the theoretical anticipation. The power consumption is approximately 3.06mW at ±1.5V supply voltages. Keywords: oscillator, CC-CCTA 1. Introduction It is well accepted that an oscillator is a basic important building circuit, which is frequently employed in electrical engineering works. Among several kinds of the oscillators, a quadrature oscillator is mostly/widely used because the quadrature oscillator can offer sinusoidal signals with 90° phase difference, as for example in telecommunications for quadrature mixers and single-sideband modulations [1]. From our survey, we found that several implementations of oscillators employing different high-performance active building blocks, such as, OTAs [2-3], four terminal floating nullors (FTFNs) [4-5], current follower [6], current controlled current differencing buffered amplifiers (CCCDBAs) [7], current controlled current differencing transconductance amplifiers (CCCDTAs) [8-9], fully- differential second-generation current conveyor (FDCCII) [10], and differencing voltage current conveyor (DVCCs) [11], have been reported. Unfortunately, these reported circuits suffer from one or more of following weaknesses: • Excessive use of the passive elements, especially external resistors [3-5, 7, 8, 11]. • Use of a floating capacitor, which is not convenient to further fabricate in IC [11] • Lack of electronic adjustability [4-6, 11]. Presently, a current-mode technique has being been more popular than voltage-mode one. This is due to operating in low-voltage environment as in portable and battery-powered equipments. Since a low-voltage operating circuit becomes necessary, the current– mode technique is ideally suited for this purpose more than the voltage-mode one. Presently, there is a growing interest in synthesizing the current-mode circuits because of more their potential advantages such as larger dynamic range, higher signal bandwidth, greater linearity, simpler circuitry and lower power consumption [12-15]. The current conveyor transconductance amplifier (CCTA) is a reported active component, especially suitable for a class of analog signal processing [16]. The fact that the device can operate in both current and voltage-modes provides flexibility and enables a variety of circuit designs. In addition, it can offer advantageous features such as high-slew rate, higher speed, wide bandwidth and simple implementation [16]. However, the CCTA cannot be controlled by the parasitic resistance at port so when it is used in some circuits, it must unavoidably require some external passive components, especially the resistors. This makes it not appropriate for IC implementation due to occupying more chip area, high power dissipation and without electronic controllability. Recently, the current-controlled CCTA (CC-CCTA) [17] has recently been proposed, it was proved that it can overcome the mentioned limitations of the CCTA. The purpose of this paper is to introduce a quadrature oscillator, based on CC-CCTAs. The oscillation condition and oscillation frequency can be adjusted with electronic method. The circuit construction consists of 2 CC-CCTAs and two grounded capacitors. In addition, either an AM or 302