Abstract: A driver apparatus for driving a load with a differential drive signal is described. For a level of input signal within a first range, a first switching driver modulates the voltage at a first output node with a first modulation index by switchably connecting at least one flying capacitor to the first output node, whilst a second switching driver modulates the voltage at a second output node with a second modulation index by controlling switching between DC voltages that are maintained throughout a switching cycle of the driver apparatus. The first and second switching drivers are controlled so, for at least a first part of the first input range, a change in input signal level results in a change of the first controlled modulation index that has a different magnitude to any change in the second controlled modulation index a constant modulation frequency of the differential drive signal is maintained.

Abstract: A system may include a front end differential amplifier having two input terminals, two input resistors, each of the two input resistors coupled to a respective one of the two input terminals, and an input common mode biasing circuit for an output stage of the front end differential amplifier, the input common mode biasing circuit comprising two current sources configured to generate currents for biasing the output stage of the front end differential amplifier.

Abstract: This application relates to methods and apparatus for driving a transducer. A transducer driver has a switch network is operable to selectively connect a driver output to any of a first set of at least three different switching voltages. which are, in use, maintained throughout a switching cycle of the driver apparatus. The switch network is also operable to selectively connect the driver output to flying capacitor driver. A controller is configured to control the switch network and flying capacitor driver to generate a drive signal at the driver output based on an input signal, wherein in one mode of operation the driver output is switched between two of the first set of switching voltages with a controlled duty cycle and in another mode of operation the driver output is connected to the flying capacitor driver which is switched between first and second states with a controlled duty cycle.

Abstract: A system may include an output power stage driver comprising a plurality of parallel-coupled field-effect transistors and a current sensor comprising a sense field-effect transistor matched to a matched field-effect transistor of the plurality of parallel-coupled field-effect transistors and gate-coupled and source-coupled to the matched field-effect transistor. The current sensor may be configured to measure a reference voltage across the sense field-effect transistor, measure a sense voltage across the matched field-effect transistor, and determine a current through the output power stage driver based on a comparison of the reference voltage to the sense voltage.

Abstract: A system may include a front end differential amplifier having two input terminals, two input resistors, each of the two input resistors coupled to a respective one of the two input terminals, and an input common mode biasing circuit for an output stage of the front end differential amplifier, the input common mode biasing circuit comprising two current sources configured to generate currents for biasing the output stage of the front end differential amplifier.

Abstract: In accordance with embodiments of the present disclosure, a system may include a buffer and a switch coupled between the buffer and a voltage supply such that the switch controls a varying voltage at a varying voltage node coupled to the buffer.

Abstract: A system may include a charge pump configured to operate in a plurality of modes including a first mode in which the ratio of an output voltage to an input voltage of the charge pump is a first ratio and a second mode in which the ratio is a second ratio and a controller configured to limit current flowing between a power source of the charge pump to the charge pump, wherein the power source provides the input voltage, by limiting a transfer of charge between the power source and the charge pump during a switching cycle of the charge pump responsive to a change in operation between modes of the plurality of modes.

Abstract: In accordance with embodiments of the present disclosure, a system may include a buffer and a switch coupled between the buffer and a voltage supply such that the switch controls a varying voltage at a varying voltage node coupled to the buffer.

Abstract: In accordance with embodiments of the present disclosure, a system may include a buffer and a switch coupled between the buffer and a voltage supply such that the switch controls a varying voltage at a varying voltage node coupled to the buffer.

Abstract: An improved Class-D amplifier may include a digital PWM modulator that receives a digital audio signal and that provides a PWM signal as an input to an analog PWM modulator of the Class-D amplifier. A digital PWM modulator may be configured to receive a digital signal and to generate a first PWM signal based on the digital signal. A digital PWM driver may be coupled to the digital PWM modulator. The digital PWM driver may be configured to receive the first PWM signal and to generate a reference PWM signal based on the first PWM signal. An analog PWM modulator may be coupled to the digital PWM driver. The analog PWM modulator may be configured to receive the reference PWM signal and to generate an output PWM signal based on the reference PWM signal.

Abstract: In accordance with embodiments of the present disclosure, a system may include a buffer and a switch coupled between the buffer and a voltage supply such that the switch controls a varying voltage at a varying voltage node coupled to the buffer.

Abstract: A system may include a charge pump configured to operate in a plurality of modes including a first mode in which the ratio of an output voltage to an input voltage of the charge pump is a first ratio and a second mode in which the ratio is a second ratio and a controller configured to limit current flowing between a power source of the charge pump to the charge pump, wherein the power source provides the input voltage, by limiting a transfer of charge between the power source and the charge pump during a switching cycle of the charge pump responsive to a change in operation between modes of the plurality of modes.

Abstract: A variable ramp up/down gain in a pre-power stage block of an audio amplifier may be used to reduce audible pops and clicks output by the audio amplifier. A controller may adjust the variable ramp up/down gain during operation of the audio amplifier. The variable ramp up/down gain may be implemented as a pulse width modulation (PWM) modulator/generator with a ramp-up and ramp-down gain under control of the controller. The variable ramp up/down gain smooths transitions of the offset between a pre-power stage block and a feedback loop and thus can reduce audible pops and clicks by reducing the offset that is amplified in the power stage block of the audio amplifier.

Abstract: A variable ramp up/down gain in a pre-power stage block of an audio amplifier may be used to reduce audible pops and clicks output by the audio amplifier. A controller may adjust the variable ramp up/down gain during operation of the audio amplifier. The variable ramp up/down gain may be implemented as a pulse width modulation (PWM) modulator/generator with a ramp-up and ramp-down gain under control of the controller. The variable ramp up/down gain smooths transitions of the offset between a pre-power stage block and a feedback loop and thus can reduce audible pops and clicks by reducing the offset that is amplified in the power stage block of the audio amplifier.