A class-D amplifier configured to adjust at least one input signal to at least one output signal. The class-D amplifier comprises: a loop filter, configured to receive the input signal; a PWM circuit, configured to generate at least one PWM signal; a summing circuit, coupled between an output of the loop filter and an input of the PWM circuit; an output circuit operating at a supply voltage, configured to generate the output signal responding to the PWM signal; and a supply voltage filter, configured to monitor the supply voltage to generate a filtered signal to the summing circuit. The summing circuit is configured to sum the output of the loop filter and the filtered signal to adjust a common-mode level of the input of the PWM circuit.

A dual-mode envelope tracking (ET) power management circuit is provided. An ET amplifier(s) in the dual-mode ET power management circuit is capable of supporting normal-power user equipment (NPUE) mode and high-power user equipment (HPUE) mode. In the NPUE mode, the ET amplifier(s) amplifies a radio frequency (RF) signal(s) to an NPUE voltage based on a supply voltage for transmission in an NPUE output power. In the HPUE mode, the ET amplifier(s) amplifies the RF signal(s) to an HPUE voltage higher than the NPUE voltage based on a boosted supply voltage higher than the supply voltage for transmission in an HPUE output power higher than the NPUE output power. The ET amplifier(s) maintains a constant load line between the NPUE mode and the HPUE mode. By maintaining the constant load line, it is possible to maintain efficiency of the ET amplifier(s) in both the NPUE mode and the HPUE mode.

Certain aspects of the present disclosure provide an amplifier for signal amplification. Certain aspects further describe methods and apparatus for applying overload protection for such amplifier. For example, one method generally includes detecting an overload condition of an amplifier based on a signal at a node of the amplifier, and controlling a parameter of an input signal of the amplifier such that the parameter of the input signal is maintained below a threshold based on the detection of the overload condition. The parameter of the input signal may include, for example, a voltage level or a duty cycle of the input signal.

Certain aspects of the present disclosure provide an amplifier for signal amplification. Certain aspects further describe methods and apparatus for applying overload protection for such amplifier. For example, one method generally includes detecting an overload condition of an amplifier based on a signal at a node of the amplifier, and controlling a parameter of an input signal of the amplifier such that the parameter of the input signal is maintained below a threshold based on the detection of the overload condition. The parameter of the input signal may include, for example, a voltage level or a duty cycle of the input signal.

Certain aspects of the present disclosure provide methods and apparatus for dynamically managing the dead time between turning on output power stage transistors in amplifiers, such as audio amplifiers. One example method of operating an amplifier generally includes generating a drive signal based on an input signal; amplifying the drive signal by alternatively driving a first transistor and a second transistor with a time between deactivating the first transistor and activating the second transistor; and adjusting the time based on a parameter of the input signal or the drive signal, during the amplifying. For example, the parameter may include an amplitude of the input signal, a duty cycle of the drive signal, or a duty cycle of a modulated signal (e.g., a pulse-width modulated signal) generated based on the input signal. The input signal may be a digital audio input signal.

Certain aspects of the present disclosure provide methods and apparatus for dynamically managing the dead time between turning on output power stage transistors in amplifiers, such as audio amplifiers. One example method of operating an amplifier generally includes generating a drive signal based on an input signal; amplifying the drive signal by alternatively driving a first transistor and a second transistor with a time between deactivating the first transistor and activating the second transistor; and adjusting the time based on a parameter of the input signal or the drive signal, during the amplifying. For example, the parameter may include an amplitude of the input signal, a duty cycle of the drive signal, or a duty cycle of a modulated signal (e.g., a pulse-width modulated signal) generated based on the input signal. The input signal may be a digital audio input signal.

A class D amplifier includes a self-oscillating class D amplification circuit that is driven by an output current signal; and a voltage-current converting circuit that outputs an output current signal in response to an input signal voltage and an output signal voltage from a feedback signal voltage.

A class D amplifier includes a self-oscillating class D amplification circuit that is driven by an output current signal; and a voltage-current converting circuit that outputs an output current signal in response to an input signal voltage and an output signal voltage from a feedback signal voltage.

A transmitter according to the present invention includes: a baseband amplitude value distribution processor (90) for changing a distribution of an amplitude value of a baseband signal based on a control signal that has been input and outputting the baseband signal as an output signal; a digital transmitter (91) that ΔΣ modulates the output signal and transmits the modulated signal; an in-band distortion measurement unit (92) for measuring an in-band distortion amount of the output signal; an amplitude value distribution measurement unit (93) for calculating an amplitude value distribution of the output signal; a sideband distortion prediction unit (94) for predicting a sideband distortion amount occurring in the output signal by the digital transmitter (91) from the calculated amplitude value distribution; and a baseband processing controller (95) for adjusting the control signal based on the measured in-band distortion amount and the sideband distortion amount and outputting the adjusted signal.

An integrated circuit includes a die that includes a circuit configured to generate a PWM signal in response to a first clock signal, and a first set of pads configured to provide amplified PWM signals to external filters. An amplifier stage is configured to provide the amplified PWM signals. The die includes two pads configured to be coupled to an external inductor, and a second set of pads configured to provide regulated voltages. An electronic converter circuit is configured to generate the regulated voltages to supply the amplifier stage. The electronic converter circuit includes a control circuit configured to drive electronic switches in response to a second clock signal to regulate the regulated voltages to a respective target value. The die includes a control block to synchronize the switching activity of the electronic switches with the switching activity of the amplifier stage.