A Rail-to-Rail Input/Output Operational Amplifier with Tracking Current Compensation

This paper presents a two-stage 2.5V CMOS operational amplifier with rail-to-rail input and output ranges. The operational amplifier achieves a constant gm with the help of simple effective current follow-up control circuit, which makes it easier to implement an optimal frequency compensation. In order to reduce the power dissipation, input differential operational pairs are biased in weak inversion. The Class-AB with voltage floating control is used as the second stage, because of which a rail-to-rail output range is achieved. The operational amplifier has a simple structure, good performance with low power and small die area.