A power amplifier circuit includes power amplifiers connected in stages to amplify a high-frequency input signal and to output an amplified high-frequency output signal, bias circuits each of which outputs a bias current to a corresponding one of the power amplifiers, and a bias control circuit configured to output a bias control current based on a second reference potential that varies in response to power of the high-frequency output signal and that is a potential of a portion in one bias circuit of the bias circuits to one or more bias circuits in a stage preceding the one bias circuit for increasing a bias current outputted from the one or more bias circuits in the stage preceding the one bias circuit.

A power amplifier includes a power splitter that splits a first signal into a second signal and a third signal, a first amplifier that amplifies the second signal within an area where the first signal has a power level greater than or equal to a first level and that outputs a fourth signal, a second amplifier that amplifies the third signal within an area where the first signal has a power level greater than or equal to a second level higher than the first level and that outputs a fifth signal, an output unit that outputs an amplified signal of the first signal, a first and a second LC parallel resonant circuit, and a choke inductor having an end to which a power supply voltage is supplied and another end connected to a node of the first and second LC parallel resonant circuits.

A matching network is a matching network of a power amplifier circuit that outputs a signal obtained by a differential amplifier amplifying power of a high-frequency signal. The matching network includes an input-side winding connected between differential outputs of the differential amplifier; an output-side winding that is coupled to the input-side winding via an electromagnetic field and whose one end is connected to a reference potential; a first LC series resonant circuit including a capacitive element and an inductive element connected in series with each other, and being connected in parallel with the input-side winding; and a second LC series resonant circuit including a capacitive element and an inductive element connected in series with each other, and being connected in parallel with the output-side winding.

A Doherty power amplifier having a main power amplification device and an auxiliary power amplification device arranged in parallel with the main power amplification device includes a load modulation circuit having a harmonic injection circuit connected with respective outputs of the main power amplification device and the auxiliary power amplification device. The harmonic injection circuit is arranged to provide a phase shift to simultaneously modulate transfer of second harmonic components generated at the main power amplification device to the auxiliary power amplification device and transfer of second harmonic components generated at the auxiliary power amplification device to the main power amplification device, when the main power amplification device and the auxiliary power amplification device are operated at saturation.

A communication device includes a power amplifier that generates power signals according to one or more operating bands of communication data, with the amplitude being driven and generated in output stages of the power amplifier. The final stage can include an output passive network that suppresses suppress an amplitude modulation-to-phase modulation (AM-PM) distortion. During a back-off power mode a bias of a capacitive unit of the output power network component can be adjusted to minimize an overall capacitance variation. A output passive network can further generate a flat-phase response between dual resonances of operation.

A power splitter that amplifies an input radio-frequency (RF) signal. The power splitter uses a single transistor in a common emitter stage of a cascode amplifier and two or more common base stages of the cascode amplifier to amplify and to split the input RF signal. A common base biasing signal can be used to simultaneously enable two or more of the common base stages to generate two or more amplified RF output signals.

An amplifier arrangement (200) for amplifying input signals and a method for operating the amplifier arrangement are disclosed. The amplifier arrangement (200) comprises a main amplifier circuit (210) having an input and an output; a first (221) and second (222) auxiliary amplifier circuits each having an input and an output, wherein each of the first (221) and second (222) auxiliary amplifier circuits being selectively operable to operate in combination with the main amplifier circuit (210). The amplifier arrangement (200) further comprises a single hybrid coupler circuit (230) having a first port (221) being coupled to the output of the main amplifier circuit (210), a second port (232) being coupled to the output of the first auxiliary amplifier circuit (221), a third port (233) being coupled to the output of the second auxiliary amplifier circuit (222) and a fourth port (234) being coupled to the load (240) of the amplifier (200).

A power amplifier includes a power splitter that splits a first signal into a second signal and a third signal, a first amplifier that amplifies the second signal within an area where the first signal has a power level greater than or equal to a first level and that outputs a fourth signal, a second amplifier that amplifies the third signal within an area where the first signal has a power level greater than or equal to a second level higher than the first level and that outputs a fifth signal, an output unit that outputs an amplified signal of the first signal, a first and a second LC parallel resonant circuit, and a choke inductor having an end to which a power supply voltage is supplied and another end connected to a node of the first and second LC parallel resonant circuits.

The present invention generally relates to a structure and method of audio amplifier by dynamic impedance adjustment, including a power amplifying unit, a loud-speaker, a current sensing unit and a subtraction unit, the power amplifying unit has a fixed closed loop gain, with an input side and an output side; the loud-speaker is electrically connected to the output side of the power amplifying unit; the current sensing unit senses the output current of the power amplifying unit, and the sensed output current is converted into a current control voltage signal; the subtraction unit inputs the audio voltage signal and the feedback current control voltage signal, and outputs the difference of the audio voltage signal minus the current control voltage signal, and inputs it to the input side of the power amplifying unit; thereby, the present invention can improve the output sound quality of the loud-speaker by dynamic impedance adjustment.

Apparatus and methods for a no-load-modulation power amplifier are described. No-load-modulation power amplifiers can comprise multiple amplifiers connected in parallel to amplify a signal that has been divided into parallel circuit branches. One of the amplifiers can operate as a main amplifier in a first amplification class and the remaining amplifiers can operate as peaking amplifiers in a second amplification class. The main amplifier can see essentially no modulation of its load between the power amplifier's fully-on and fully backed-off states. The power amplifiers can operate in symmetric and asymmetric modes. Improvements in bandwidth and drain efficiency over conventional Doherty amplifiers are obtained. Further improvements can be obtained by combining signals from the amplifiers with hybrid couplers.