A compact sub-1V class AB operational amplifier for low-voltage switched-capacitor circuits

A compact sub-1V class-AB operational amplifier to be used as a building block for low-voltage switched-capacitor architectures is presented. The proposed amplifier works properly with supply voltages in the range 0.9 V-1.4 V, providing a gain-bandwidth product of 8 MHz, and a maximum output short-circuit current of 1 mA with 120 μA quiescent supply current. The performances of the operational amplifier are demonstrated by means of electrical simulations performed on a prototype designed with the UMC 0.18 μm / 3.3 V process. The total area of the cell, estimated from a preliminary layout, is 75×105 μm ² .