A circuit configured to amplify a signal from which an offset is cancelled includes an amplifier including an input stage configured to receive an input signal, the amplifier configured to amplify the input signal and output the amplified signal, and a switch including a transistor configured to reset the amplifier in response to a reset signal, the transistor including a body node connecting the transistor to the circuit, the transistor being configured to form a current path between the body node of the transistor and the input stage of the amplifier.

Methods, apparatus, and systems are disclosed that adjust transient response in a multistage system. An example apparatus includes a first filter including an input configured to be coupled to an output of a master stage, an amplifier, the first input of the amplifier coupled to the input of the first filter, the second input of the amplifier coupled to the output of the first filter, a second filter, the input of the second filter coupled to the output of the amplifier, and a comparator, the first input of the comparator coupled to the input of the first filter circuit, the second input of the comparator coupled to the output of the amplifier, the third input of the comparator coupled to the output of the second filter, and the output of the comparator adapted to be coupled to a latch.

Methods, apparatus, and systems are disclosed that adjust transient response in a multistage system. An example apparatus includes a first filter including an input configured to be coupled to an output of a master stage, an amplifier, the first input of the amplifier coupled to the input of the first filter, the second input of the amplifier coupled to the output of the first filter, a second filter, the input of the second filter coupled to the output of the amplifier, and a comparator, the first input of the comparator coupled to the input of the first filter circuit, the second input of the comparator coupled to the output of the amplifier, the third input of the comparator coupled to the output of the second filter, and the output of the comparator adapted to be coupled to a latch.

A power control system for audio power amplifiers, especially in the automotive segment, dynamically controlling the output voltage through the reading of the input and output currents, and other parameters, automatically adjusting the amplifier to the load and to the operation conditions, allowing that the amplifier always operates within the safe operation range.

An apparatus and method for calibrating an envelope tracking (ET) lookup table (LUT) are provided. An ET power management apparatus includes a power amplifier configured to amplify a radio frequency (RF) signal from a time-variant input power to a time-variant output power linearly related to the time-variant input power. A calibration circuit is employed to receive a time-variant output power feedback nonlinearly related to the time-variant input power, determine a linear relationship between the time-variant input power and the time-variant output power based on the time-variant output power feedback, and calibrate the ET LUT based on the determined linear relationship. As a result, it is possible to improve accuracy of the ET LUT to thereby improve operating efficiency and linearity of the power amplifier.

A push-pull radio frequency power amplifier includes a coupling feedback circuit, a drive stage circuit and a power output stage circuit, in which the coupling feedback circuit is connected with the drive stage circuit and/or the power output stage circuit; the coupling feedback circuit is configured to generate an alternating voltage at an input end of a first transistor and/or an input end of a push-pull transistor; when the alternating voltage and a voltage at the input end are in a same direction, a positive feedback of an input signal at the input end is achieved; and the first transistor represents a transistor in the drive stage circuit and the push-pull transistor represents a second transistor and a third transistor that form a push-pull structure in the power output stage circuit.

A bias circuit includes a mirror current source and a current-to-voltage converter. A first terminal of the mirror current source is connected to a supply voltage terminal, a second terminal of the mirror current source is connected to a reference voltage terminal, and a third terminal of the mirror current source is connected to the current-to-voltage converter. A mirror current source is configured to acquire a supply voltage transmitted at the supply voltage terminal through the first terminal, acquire a reference voltage transmitted at the reference voltage terminal through the second terminal, and regulate the supply voltage by using the reference voltage and a preset parameter to obtain a mirror current corresponding to the supply voltage. The preset parameter is parameter information of the mirror current source. The current-to-voltage converter is configured to convert the mirror current into a voltage to provide a bias voltage based on the voltage.

A bias circuit includes a mirror current source and a current-to-voltage converter. A first terminal of the mirror current source is connected to a supply voltage terminal, a second terminal of the mirror current source is connected to a reference voltage terminal, and a third terminal of the mirror current source is connected to the current-to-voltage converter. A mirror current source is configured to acquire a supply voltage transmitted at the supply voltage terminal through the first terminal, acquire a reference voltage transmitted at the reference voltage terminal through the second terminal, and regulate the supply voltage by using the reference voltage and a preset parameter to obtain a mirror current corresponding to the supply voltage. The preset parameter is parameter information of the mirror current source. The current-to-voltage converter is configured to convert the mirror current into a voltage to provide a bias voltage based on the voltage.

A power amplifier circuit includes: a transistor which is supplied at a base with a bias current, amplifies an input signal, and outputs a current; a transistor which is connected at a base to the base of the transistor and in which a current commensurate with the current is input to a collector; a transistor which outputs a bias control signal which controls supply of the bias current; and a control circuit which is connected to the collector of the transistor and a gate of the transistor and controls a bias control signal on the basis of a reference current based on a reference signal and the current.

A wideband envelope modulator comprises a direct current (DC)-to-DC switching converter connected in series with a linear amplitude modulator (LAM). The DC-DC switching converter includes a pulse-width modulator that generates a PWM signal with modulated pulse widths representing a time varying magnitude of an input envelope signal or a pulse-density modulator that generates a PDM signal with a modulated pulse density representing the time varying magnitude of the input envelope signal, a field-effect transistor (FET) driver stage that generates a differential PWM or PDM drive signal, a high-power output switching stage that is driven by the PWM or PDM drive signal, and an output energy storage network including a low-pass filter (LPF) of order greater than two that filters a switching voltage produced at an output switching node of the high-power output switching stage.