High performance class AB operational amplifier

摘要

A class AB operational amplifier includes an input stage, an output stage and a level shifter stage to control the quiescent current of the output stage and to transfer the signal from the input stage to the output stage, and a control circuit of the level shifter stage. The control circuit includes a transistor differential pair having a differential input terminals and the differential voltage at the differential terminals of the differential pair controls the level shifter stage.

主权项

1. A class AB operational amplifier comprising an input stage, an output stage and a level shifter stage adapted to control the quiescent current of the output stage and to transfer the signal from the input stage to the output stage, a control circuit of the level shifter stage, characterized in that the control circuit comprises at least one transistor differential pair having differential input terminals, said control circuit being configured so that the differential voltage at the differential terminals of the transistor differential pair controls the level shifter stage, characterized in that said control circuit comprises circuit means coupled with the input terminals of the transistor differential pair and wherein a first bias current flows, the control circuit being configured to control the quiescent current to be proportional to the amount of said first bias current, and characterized in that the level shifter stage comprises at least a first and a second intermediate transistors coupled in series by means of an impedance and the series being arranged between a first and a second reference voltage, the voltage across the impedance being said differential voltage at the differential input terminals of the transistor differential pair.