Operational transconductance amplifier with rail-to-rail input stage using single channel type MOSFETs

This paper proposes a novel method to realize an input stage for a rail-to-rail operational transconductance amplifier (OTA). The proposed input stage consists of single channel type MOSFETs. Therefore no matching is necessary between n-channel MOSFETs and p-channel MOSFETs unlike conventional methods. The proposed input stage is composed of three MOSFETs which operate in plural operation regions. Nevertheless a combination of drain currents of the three MOSFETs is proportional to an input voltage which varies between two power-supply rails. A circuit configuration to realize a rail-to-rail OTA with the proposed input stage is also proposed. The operation principle and the validity of the proposed circuit are confirmed through HSPICE simulations.