Fully Differential Amplifier Topology to Drive Dynamic Speakers in Class AB Mode
AssigneeDialog Semiconductor GmbH
InventorZakaria Mengad
Life of this patent
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Abstract
Circuits and methods to achieve a new fully differential amplifier topology in class AB mode are disclosed. In a preferred embodiment of the disclosure the differential amplifier is diving dynamic speakers. An differential intermediate stage combines four different feedbacks, all sharing four high impedance nodes: main loop regulation feedback, common mode regulation feedback, and output stage quiescent current regulation for both differential output stage branches.
Claims24
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 each output branch comprising high side and low side devices, wherein the amplifier comprises an output stage and an intermediate stage processing the input signals;
- (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.
A circuit of a fully differential amplifier operating in class AB mode, comprising:
- a differential output stage comprising a P and an M branch, wherein each branch comprises a high side device and a low side device;
- a differential intermediate stage comprising
- a first pair of PMOS transistors comprising a first and a second PMOS transistor, amplifying a differential input error signal wherein each transistor generates a driving signal for a correspondent said low side device and a control signal to a correspondent said high side device, wherein the sources of both transistors are connected;
- a first pair of NMOS transistors wherein a gate of each NMOS transistor is connected at a correspondent high impedance node to a drain of a correspondent transistor of the first pair of PMOS transistors and to a gate of said low side device and a drain of each NMOS transistor is connected to a drain and a gate of a correspondent NMOS transistor of a third pair of NMOS transistors;
- said second pair of PMOS transistors, wherein each gate of the second pair of PMOS transistors is connected to a gate of a correspondent high side device forming a current mirror, wherein the each of the PMOS transistors of the second pair are scaled down in a same scale relative to the high side devices;
- a loop control circuit;
- a common mode regulation loop circuit;
- and
- a class AB regulation loop.
Dependencies are inferred from the claim text.