Differential operational transconductance amplifier

摘要

A low-power dual-gm differential operational transconductance amplifier (OTA) having a differential input for improved common-mode noise rejection, a high transconductance for power savings, and circuitry for controlling its output conductance. The OTA includes a pair of input inverters for receiving differential input signals, a common-mode voltage control circuit for controlling the DC voltage levels of the inverters, and a Q-control circuit for adjusting the OTA's output conductance. The common-mode voltage control circuit has a pair of compensating current sources and a feedback loop acting as a high-gain amplifier. The high-gain amplifier has a pair of comparators for respectively comparing the DC voltage levels of the inverter outputs with a reference voltage. The Q-control circuit includes a current source coupled to a crossed-coupled NMOS transistor pair such that the OTA's output conductance may be controlled by adjusting the current source.