Super Class AB OTAs Based on Low-Power Adaptive Techniques at the Input Stage and the Active Load

Two novel topologies of single-stage Super Class AB Operational Transconductance Amplifiers (OTAs) are presented. They are based on a novel technique to achieve a double current boosting: The differential input stage operates in Class AB by means of adaptive biasing techniques, and the active load provides additional dynamic current boosting using nonlinear current mirrors. The OTAs combine excellent performance with simplicity of design and suitability for low-voltage battery-powered applications. Experimental results for a test chip prototype fabricated in a standard 0.5-m CMOS technology are presented, using a dual supply voltage of ±1-V and 10-A bias currents. They confirm essential improvement of slew rate and gain-bandwidth product over a conventional Class A OTA with the same supply voltage and bias currents.