Importance

Loading Importance Indicators...

Abstract

An operational amplifier input stage includes two transistors coupled as a differential amplifier to receive input signals. At least one transistor is stacked in a load circuit of each input transistor for the purpose of lowering the voltage across each transistor. In order to eliminate the effects of error currents resulting from conventional resistor self biasing of the stacked transistors, two nodes, to which the input transistors are coupled, are identified. According to a first embodiment, feedback circuits are coupled to each node and each feedback circuit maintains the coupled node at a voltage level established by the feedback apparatus of the operational amplifier. According to a second embodiment, a single feedback circuit controls the voltage at a first node and the same feedback circuit maintains the voltage level of a second node at a constant level. Either feedback circuit eliminates circuit drift and offset voltage changes resulting from changes in common mode and/or power supply voltages by eliminating the effects of resistive loading on the input stage components.

Loading the Abstract Image...

First Claim