A New Design Technique for Rail-to-Rail Amplifiers

Abstract — A design technique for rail-to-rail operational amplifiers is presented. The technique adds dummy pairs to sense the common mode range of the input differential pair and adjusts the output current accordingly. An amplifier built in the TSMC 0.25μ process shows a DC gain of approximately 84dB. The amplifier provides high gain for a wider range of output voltages. Design considerations for reducing the impact of the additional circuitry on the core are provided. The technique described can be adapted for use with traditional fully-differential rail-to-rail amplifiers. I