Highly linear operational transconductance amplifier with low transconductance

摘要

An operational transconductance amplifier (OTA) with improved linearity and improved dynamic range operating on a single five-volt supply. The OTA comprises a virtual ground circuit, a current diverting portion for diverting current through first and second paths to the virtual ground circuit substantially proportional to a differential input voltage, a resistive portion, a current mirror for mirroring currents in the first and second paths into third and fourth paths, respectively, and output stage biasing for providing differential output currents. The resistive portion comprises first and second saturated MOS transistors, the voltage-current characteristics of the MOS transistors making them operate as large-valued resistors because of the short channel effect. The saturated MOS transistors improve linearity and dynamic range by decreasing the variation in output current caused by fluctuations in input voltage. In one form, the current mirror portion is implemented using PNP bipolar transistors.