A power converter produces power at a greater voltage than provided by a power source, while drawing power from the power source, wherein the power converter has a variable input current limit or a variable input power limit. One or more audio amplifiers are configured into i) drawing power from the power source bypassing the power converter and ii) drawing power from the power converter, according to audio signal amplitude, during audio playback and in accordance with an audio signal being amplified. A load of each amplifier is determined for when the amplifier is drawing power from the power source bypassing the power converter. The variable input limit of the power converter is adjusted in accordance with the determined load, during the audio playback. Other aspects are also described and claimed.

A multi-band power amplifier module includes at least one transmission input terminal, at least one power amplifier circuit that receives a first transmission signal and a second transmission signal through the at least one transmission input terminal, a first filter circuit that allows the first transmission signal to pass therethrough, a second filter circuit that allows the second transmission signal to pass therethrough, at least one transmission output terminal through which the first and second transmission signals output from the first and second filter circuits are output, a transmission output switch that outputs each of the first and second transmission signals output from the at least one power amplifier circuit to the first filter circuit or the second filter circuit, and a first tuning circuit that adjusts impedance matching between the at least one power amplifier circuit and the at least one transmission output terminal.

An improved method of providing high burst power to audio amplifiers from limited power sources, using parallel power paths to increase system efficiency without need for a power path controller, thus utilizing a simplified circuit operation and maximizing average power available for both the amplifier and supporting circuitry.

Power amplification system with adjustable common base bias. A power amplification system can include a cascode amplifier coupled to a radio-frequency input signal and coupled to a radio-frequency output. The power amplification system can further include a biasing component configured to apply one or more biasing signals to the cascode amplifier, the biasing component including a bias controller and one or more bias components. Each respective bias component may be coupled to a respective bias transistor.

Apparatus and methods for power amplifiers with positive envelope feedback are provided herein. In certain implementations, a power amplifier system includes a power amplification stage that amplifies a radio frequency signal, at least one envelope detector that generates one or more detection signals indicating an output signal envelope of the power amplification stage, and a wideband feedback circuit that provides positive envelope feedback to a bias of the power amplification stage based on the one or more detection signals. The power amplifier system further includes a supply modulator that controls a voltage level of a supply voltage of the power amplification stage based on the one or more detection signals such that the supply voltage is modulated with the output signal envelope through positive envelope feedback.

An amplifier circuit includes a driver amplifier implemented on a silicon-on-insulator (SOI) substrate and configured to amplify a radio frequency (RF) signal, a bypass circuit implemented on the SOI substrate and configured to selectively bypass the driver amplifier, an output coupled to the driver amplifier and the bypass circuit, an interconnect configured to couple the output to a gallium arsenide (GaAs) substrate, and a power amplifier implemented on the GaAs substrate and configured to amplify a signal received over the interconnect from the output.

A power amplifier module includes an amplifier transistor and a bias circuit. A first power supply voltage based on a first operation mode or a second power supply voltage based on a second operation mode is supplied to the amplifier transistor. The amplifier transistor receives a first signal and outputs a second signal obtained by amplifying the first signal. The bias circuit supplies a bias current to the amplifier transistor. The bias circuit includes first and second resistors and first and second transistors. The first transistor is connected in series with the first resistor and is turned ON by a first bias control voltage which is supplied when the first operation mode is used. The second transistor is connected in series with the second resistor and is turned ON by a second bias control voltage which is supplied when the second operation mode is used.

A power amplifier circuit includes: a first differential amplifier that amplifies a first signal split from the input signal and outputs a second signal; a second differential amplifier that amplifies a third signal split from the input signal and outputs a fourth signal; a first transformer including a first input-side winding to which the second signal is input and a first output-side winding; a second transformer including a second input-side winding to which the fourth signal is input and a second output-side winding; a first phase conversion element that is connected in parallel with the first output-side winding and outputs a fifth signal; and a second phase conversion element that is connected in parallel with the second output-side winding and outputs a sixth signal. The first and second output-side windings are connected in series and output a signal obtained by adding voltages of the fifth and sixth signals together.

According to some implementations, a power amplifier (PA) includes a common emitter configured to receive a radio-frequency (RF) signal. The PA also includes a carrier amplifier coupled to the common emitter to form a carrier cascode configuration, a collector of the carrier amplifier provided with a first supply voltage. The PA further includes a peaking amplifier coupled to the common emitter to form a peaking cascode configuration, a collector of the peaking amplifier provided with a second supply voltage greater than the first supply voltage.

A Doherty amplifier includes a carrier amplifier, a peaking amplifier, and a phase compensation circuit. The carrier amplifier 11 includes a main amplifying element and a parasitic element, and the peaking amplifier includes an auxiliary amplifying element and a parasitic element. The phase compensation circuit has a negative electrical length that allows a total electrical length of a signal transmission path starting from an output source of the main amplifying element to a power combiner to become 180N90 where N is a positive integer. In addition, a signal transmission path starting from an output source of the auxiliary amplifying element to the power combiner has an electrical length of 180M180 where M is a positive integer.