Abstract—In this paper a precision full-wave rectifier of minimal configuration is presented. The main structure employs only single second-generation current conveyor and two diodes. It enables to process both low-voltage and low-current signals. The proposed circuit is able to rectify signals up to 500 kHz and beyond with no or small distortion. If the voltage or current biasing scheme is used the frequency range can be further extended. Using the CMOS structure of the current conveyor, the behavior of proposed full-wave rectifier has been verified by SPICE simulations. Furthermore, using the universal current conveyor UCC-N1B 0520 experimental measurements are also presented. Keywords—analog processing circuits, CMOS, current conveyors, instrumentation, precision full-wave rectifier. I. INTRODUCTION N INSTRUMENTATION and measurements the precise rectification function is of great importance since it is utilized in applications such as ac volt- and ampere-meters, signal-polarity detectors, peak value measurement, or averaging circuits [1]. Because of the threshold voltage of the diodes, simple passive rectifiers operate inaccurately with small signals. Therefore, precision rectifiers containing active elements have to be used. Conventional precision rectifiers based on voltage feedback amplifiers (op amps) suffer from the finite slew rate and effects caused by the diode commutation [1]. These circuits operate well only at low frequencies and cause considerable waveform distortions already above 1 kHz [2], [3]. Significant improvement in high frequency signal rectification has been achieved by using active elements with high-impedance current outputs, to which the diodes are connected. In [4]-[7] the same voltage-mode full-wave rectifier using two second- generation current conveyors and four diodes is presented, which can be used to process signals at frequencies up to 100 kHz. The frequency range can be further extended using the voltage [4], [7] or current [6], [7] biasing scheme. In [8] and [9] full-wave rectifiers are proposed that employ second- generation current conveyor, bipolar current mirrors and three Manuscript received September 29, 2010. This work was supported in part by the Czech Science Foundation projects no. P102/10/P561 and no. P102/09/1681, by BUT project no. FEKT-S-10-16, and by research project no. MSM0021630513. J. Koton, N. Herencsar and K. Vrba are with the Department of Telecommunications, Brno University of Technology, Purkynova 118, 612 00 Brno, Czech Republic, (tel.: +420 541 149 190 , fax.: +420 541 149 192, e-mails: {koton, herencsn, vrbak}@feec.vutbr.cz). or two resistors. Here, neither voltage nor current biasing scheme can be used and therefore the rectified signals can be at frequencies up to 100 kHz. A voltage-mode full-wave rectifier using dual-X current conveyor is presented in [10], where the required diodes are suitably replaced by NMOS transistors. Another precise full-wave rectifier is presented in [11]. The structure uses the standard op amp bases rectifier (Fig. 2a), where the OPA1 is replaced by operational conveyor and later by second-generation current conveyor [3]. In this paper new current conveyor based precision full- wave rectifier is presented. If it operates in current-mode, only single active element and two diodes are to be used. For voltage-mode operation additional resistors are connected that represent simple voltage-to-current and current-to-voltage convertors. The behavior of the proposed precise full-wave rectifier has been verified both by SPICE simulations and by experimental measurements. II. CURRENT CONVEYOR A current conveyor is generally a three- (or four-) terminal active device. It has one low-impedance current input X, one high-impedance voltage input Y and one or more high- impedance current outputs Z. The current conveyor was introduced in 1968 for the first time [12] and labeled as first- generation current conveyor CCI. Later, the second- (CCII) [13] and third-generation current conveyors [14] (CCIII) were presented. These active elements receive considerable attention and are used in applications where the wide frequency bandwidth or output current response is necessary. Even if different generations are described nowadays, the most often used one is the CCII and other types from it derived, e.g. electronically tunable CC [15], current controlled CC [16], differential difference CC [17], differential voltage CC [18], universal CC [19] can be mentioned as examples. The relation between the currents and voltages of a four-terminal CCII (Fig. 1) is described by following set of equations: X Y v v = , Y 0 i = , Z+ X i i = , Z X i i − =− . (1) Fig. 1 Circuit symbol of four-terminal CCII Minimal Configuration Versatile Precision Full- Wave Rectifier Using Current Conveyors Jaroslav Koton, Norbert Herencsar, and Kamil Vrba I Advances in Communications, Computers, Systems, Circuits and Devices ISBN: 978-960-474-250-9 111