Improved class-AB output stage for Sub-1 V fully-differential operational amplifiers

An existent architecture for low voltage class-AB output stages is analyzed finding critical issues for which effective original solutions are proposed. The approach has been applied to the design of a compact class-AB fully-differential operational amplifier, capable of operating at a supply voltage of 0.8 V, providing a maximum output current of 7.5 mA with only 156 uA of quiescent supply current. The proposed amplifier constitutes a convenient building block for switched-capacitor circuits and low-voltage sensor interfaces. The performances of the amplifier are demonstrated by means of electrical simulations performed on a prototype designed with the UMC 0.18 um CMOS process. The total estimated area of the cell is 0.023 mm
²
.