Differential driver having input signal-controlled common-mode reference

A system for providing a power output to a load, comprising:

• an output stage for supplying the current to the load, the output stage having a first push-pull driver coupled to a first output for coupling to a first terminal of the load and a second push-pull driver coupled to a second output for coupling to a second terminal of the load;
• a mode selection control circuit for selecting between a pulse-width modulated mode and a linear mode of the system;
• a pulse-width modulator output driver for providing pulse-width modulated drive signals to an input of the output stage when the mode selection control circuit selects the pulse-width modulated mode;
• and
• a linear amplifier stage for providing a linear analog signal to the input of the output stage when the mode selection control circuit selects the linear mode, wherein both the first push-pull driver and the second push-pull driver are operated to supply the current to the load when the mode selection control circuit selects the linear mode, wherein the linear amplifier stage comprises a driver circuit having a first output for driving a first output of the differential amplifier, a second output for driving a second output of the differential amplifier, a first input for receiving a first drive signal, a second input for receiving a second drive signal, and at least one third input for receiving a common-mode reference signal, and wherein the second output is a complementary output to the first output of the driver circuit, wherein the linear amplifier stage further comprises a signal maxima detector having a differential input for receiving the first drive signal and the second drive signal, wherein the maxima detector detects a maximum value of the first drive signal and the second drive signal including any common-mode voltage of the first drive signal and the second drive signal, and wherein the linear amplifier stage comprises a common-mode reference circuit having an output for providing the common-mode reference signal and an input coupled to an output of the signal maxima detector, whereby a common-mode voltage of the first output of the driver circuit and the second output of the driver circuit are independent of one or more power supply voltages provided to the driver circuit.

A method of generating a differential output drive signal, comprising:

• receiving a differential drive signal having an input common-mode voltage and composed of a first drive signal and a second complementary drive signal;
• generating a common-mode reference by detecting an instant maximum voltage of the first drive signal and the second complementary drive signal and generating a time-varying common-mode reference signal from the detected instant maximum voltage;
• and
• driving a first output of a driver circuit of a differential amplifier with the first drive signal and a second output of the driver circuit with the second drive signal, wherein the first output and second output have a common-mode voltage controlled by the common-mode reference signal and differential outputs controlled by the first drive signal and the second drive signal, whereby a common-mode voltage of the first output of the driver circuit and the second output of the driver circuit are independent of one or more power supply voltages provided to the driver circuit.