A highly linear operational transconductance amplifier for large signal operations

Operational Transconductance Amplifiers (OTA´s) with linear input-output characteristics have become a focus of interest for analogue continuous-time circuits such as filters. This paper introduces a new principle for a CMOS-OTA circuit with excellent linearity. It overcomes the restrictions of known concepts, in that its linear input-output transfer characteristic is not influenced by the MOS threshold voltage dependence on the source-substrate voltage or other effects. As the internal signal paths are very short, high action speed is obtained. The circuit can be implemented with a double or a single-ended output stage. Due to symmetrical internal signal paths, best results in terms of linearity, PSRR, and CMRR, are obtained in combination with a double-ended output stage. The proposed principle has been successfully incorporated in applications such as filters, and (dB-linear voltage controlled) amplifiers. To give an impression of the obtainable performance with the proposed principle, some significant simulated and measured characteristics of the manufactured test circuits are discussed