Reconfigurable output baluns for wideband push-pull amplifiers are disclosed. In certain embodiments, a mobile device includes a transceiver that generates a first radio frequency signal of a first frequency band and a second radio frequency signal of a second frequency band, and a front-end system including a push-pull power amplifier that selectively amplifies one of the first radio frequency signal or the second radio frequency signal based on a band control signal. The push-pull power amplifier includes an input balun, an output balun, and a pair of amplifiers coupled between the input balun and the output balun. The band control signal is operable to control an impedance of the output balun.

The present invention provides an amplifier system including an audio amplifier and a power converter. The audio amplifier is supplied by at least a first supply voltage and a second supply voltage, and the audio amplifier is configured to receive an audio signal to generate an output signal. The power converter includes only one inductor, and is configured to generate the first supply voltage and the second supply voltage according to an input voltage.

An integrated circuit includes an oscillator and a power amplifier. The oscillator includes a first node, a second node, and a network of one or more reactive components coupled between the first node and the second node. The power amplifier includes a first input coupled to the first output of the oscillator, a second input coupled to the second output of the oscillator, and an output. The power amplifier includes a coarse gain control circuit, a first amplifier stage, and a second amplifier stage.

A heterojunction bipolar transistor includes a collector layer, a base layer, and an emitter layer that are stacked on a substrate. The collector layer includes a graded semiconductor layer in which an electron affinity increases from a side closer to the base layer toward a side farther from the base layer. An electron affinity of the base layer at an interface closer to the collector layer is equal to an electron affinity of the graded semiconductor layer at an interface closer to the base layer.

One example includes a device that is comprised of a pre-power amplifier, a power amplifier, a signal path, and a dynamic bias circuit. The pre-power amplifier amplifies an input signal and outputs a first amplified signal. The power amplifier receives the first amplified signal and amplifies the first amplified signal based on a dynamic bias signal to produce a second amplified signal at an output thereof. The signal path is coupled between an output of the pre-power amplifier and an input of the power amplifier. The dynamic bias circuit monitors the first amplified signal, generates the dynamic bias signal, and outputs the dynamic bias into the signal path.

An RF power detector adapted to detect an RF power of an RF signal, includes, in part, an antenna adapted to receive the RF signal, a narrow-band RF power converter adapted to convert the RF signal to a DC signal, an accelerometer, and a magnetometer. The accelerometer and magnetometer are adapted to determine the orientation and location of the power detector. The power detector optionally includes a gyroscope. The narrow-band RF power converter may be a rectifier tuned to the frequency of the RF signal. The power detector optionally includes an indicator adapted to provide information representative of the amount of the DC power of the DC signal, as well as position and orientation of the power detector. The power detector may be adapted to be inserted into a mobile device so as to provide the information about the amount of DC power, orientation and position to the mobile device.

An RF power detector adapted to detect an RF power of an RF signal, includes, in part, an antenna adapted to receive the RF signal, a narrow-band RF power converter adapted to convert the RF signal to a DC signal, an accelerometer, and a magnetometer. The accelerometer and magnetometer are adapted to determine the orientation and location of the power detector. The power detector optionally includes a gyroscope. The narrow-band RF power converter may be a rectifier tuned to the frequency of the RF signal. The power detector optionally includes an indicator adapted to provide information representative of the amount of the DC power of the DC signal, as well as position and orientation of the power detector. The power detector may be adapted to be inserted into a mobile device so as to provide the information about the amount of DC power, orientation and position to the mobile device.

Apparatus and methods for a low-load-modulation power amplifier are described. Low-load-modulation power amplifiers can include 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 low modulation of its load between the power amplifier's fully-on and fully backed-off states. Improvements in bandwidth and drain efficiency over conventional Doherty amplifiers are obtained.

Apparatus and methods for a low-load-modulation power amplifier are described. Low-load-modulation power amplifiers can include 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 low modulation of its load between the power amplifier's fully-on and fully backed-off states. Improvements in bandwidth and drain efficiency over conventional Doherty amplifiers are obtained.

Embodiments of RF amplifiers and packaged RF amplifier devices each include an amplification path with a transistor die, and an output-side impedance matching circuit having a T-match circuit topology. The output-side impedance matching circuit includes a first inductive element (e.g., first wirebonds) connected between the transistor output terminal and a quasi RF cold point node, a second inductive element (e.g., second wirebonds) connected between the quasi RF cold point node and an output of the amplification path, and a first capacitance connected between the quasi RF cold point node and a ground reference node. The RF amplifiers and devices also include a baseband termination circuit connected to the quasi RF cold point node, which includes an envelope resistor, an envelope inductor, and an envelope capacitor coupled in series between the quasi RF cold point node and the ground reference node.