I. Introduction The use of nonlinear load power electronic component connected to power systems cause harmonic currents and harmonic voltages. Harmonics are the major source of waveform distortion, the harmonic control in electric power system has been described in IEEE 519-1992 [3]. Active Power Filters (APFs) are the new trend in harmonic filtering technology that can be used to eliminate harmonic currents and voltages. APFs are operated dynamically which are more flexible than the use of passive filters that normally carried out static operating conditions. There are hundreds of research papers topic of APF have been reviewed as shown in [5]. The control of APF has been developed for decades, known as a part of Static Var Compensator (SVC). As discussed in [8], OTA (Operational Transconductance Amplifier) [1], [2] is the adaptive device that implemented for adaptive circuit and used for mixed-signal adaptive control and real-time processing control of APF. OTA&CCII-based circuit has been introduced on MATLAB model as discussed in [9], the simulation results show that the parameter used in MATLAB model can be applied to the design of controller of the control blocks using off-the-shelf OTA device, LM13700 in this paper. The most common control strategy for APF that widely used is based on “p-q theory” in the time- domain which using digital controller [6], [13],[14] since it gives more flexibly for many control algorithms. However, since the front- end of the digital controller requires DAC/ADC component which cause conversion time delay so that the switching frequency is limited. The Neural Network method [10] and frequency analysis method, using FFT, [11] is proposed for new algorithm. The hardware FPGA controller [7], [12], [16], [17] is proposed instead of DSP to give simpler implementation, however, the A/D Converter is still required which gives the delay time computation. The sliding mode Abstract: - This paper presents a mixed-signal controller of shunt active power filter using OTA (Operational Transconductance Amplifier) – based circuit for the control of active power filter (APF). The advantage of using OTA-based circuits is its adaptive control, real- time processing which can work with the high frequency power switches. The results show that OTA-based circuit can be used for the controller of APF which is simpler design compared to DSP, moreover, it can be fabricated in one single chip by using CMOS technology. Theoretical analysis, design and computer simulation results are provided. Key-Words : OTA, simple controller, mixed-signal, circuits, Shunt, Active Power Filter SOMBAT VANICHPRAPA 1 , CHERDCHAI PRAPANAVARAT , BOONRUK CHIPIPOP 1 1. Department of Computer Engineering, King Mongkut’s University of Technology Thonburi , Thailand 2. Department of Electrical Engineering , King Mongkut’s University of Technology Thonburi, Thailand sombat@ieee.org PERFORMANCE OF A SIMPLE MIXED-SIGNAL CONTROLLER OF SHUNT ACTIVE POWER FILTER USING OTA-BASED CIRCUIT RECENT ADVANCES in NETWORKING, VLSI and SIGNAL PROCESSING ISSN: 1790-5117 67 ISBN: 978-960-474-162-5