Patent ID: 8674765
Filing Date: 2014-03-18
Classification: H03F

Abstract:
1. A method to achieve a fully differential amplifier operating in class AB mode, comprising an arrangement for differential drive intermediate stage to control a differential loop, a common mode regulation and class AB regulation, comprising the following steps: (1) providing a fully differential amplifier operating in class AB mode comprising ports for differential input error signals Vip and Vim and for differential output signals Vop and Vom, wherein Vop is generated by a first output branch and Vom is generated by a second output branch, wherein the output branches are arranged in parallel between supply rails, wherein each output branch comprising high side and low side devices, and wherein the amplifier comprises an output stage and an intermediate stage processing the input signals and a power stage; (2) enabling differential output regulation by introducing dual differentiation of the input error signal to support common mode regulation by splitting driving signals for a first transistor of each of said output branch from a control path for a second transistor of each of said output branch; (3) reducing a common mode error by decreasing both voltages Vop and Vom if a differential output common mode is higher than a common mode reference; and (4) regulating quiescent currents of both output branches inside the amplifier by sensing a current of a device of each output branch conducting the smallest current, comparing it with an internal reference current in order to regulate the minimum current.