A proposal for high-performance CCII-based analogue CMOS design

A novel fully differential CMOS second-generation current conveyor (CCII) topology is presented. It can be considered as a universal fully differential programmable active element. The circuit operates in moderate inversion region, and features high linearity over a wide input range. Current gain between terminals X and Z can be continuously tuned in a wide range. These features are essential to extend the utilization of CCII-based circuits to high-performance VLSI applications. Analogue design based on this new cell is illustrated by various examples. The proposed CCII has been fabricated in a 0.5-µm CMOS technology and its main performance characteristics have been measured. They are in good agreement with theory and demonstrate that operation in moderate inversion can lead to distortion levels much lower than those achieved in strong inversion. Experimental results for a Tow–Thomas biquadratic filter fabricated on the same chip are also presented, showing continuous frequency tuning in more than a decade.