A -90 dB THD rail-to-rail input opamp using a new local charge pump in CMOS

This paper describes the principle and design of a CMOS Rail-to-Rail input operational amplifier with THD performance of -90 dB. The operation of the opamp is based on a standard two-stage Miller configuration and is capable of driving a low ohmic load (32 Ω). THD levels below -90 dB has not yet been shown with existing Rail-to-Rail techniques. The Rail-to-Rail functionality is achieved with a new area efficient on chip charge pump circuit for the generation of the supply voltage for the input differential pair.