Input/output rail-to-rail video op-amp with constant behaviour over the entire voltage range

This paper introduces a two-stage operational amplifier with input/output rail-to-rail swing capability and constant transconductance and slew-rate over the entire voltage range. The input stage provides, simultaneously, constant small-signal and large-signal responses, whilst imposing no appreciable constraint for high-frequency operation. A class-AB output stage with an accurate control of the quiescent current has been included to ensure rail-to-rail output swing. The circuit has been designed to operate with a 3-V single supply and has been fabricated in standard 0.8 /spl mu/m CMOS technology. Experimental results showed a gain-bandwidth product larger than 17 MHz and a high-drive capability, which ensures output rail-to-rail operation with resistive loads as low as 560 /spl Omega/. Maximum deviations in the amplifier large and small-signal responses are maintained within /spl plusmn/3.5% and /spl plusmn/4.6%, respectively.