Abstract: Apparatus and methods for saturation detection of power amplifiers are provided. In certain embodiments, a power amplifier system includes a carrier amplifier including a first capacitor and a first gain bipolar transistor having a base configured to receive a radio frequency signal through the first capacitor. The power amplifier system further includes a saturation detector including a resistor and a detection bipolar transistor that is located within 20 ?m of the first gain bipolar transistor. The detection bipolar transistor has a base connected to the base of the first gain bipolar transistor through the resistor and a collector that generates a saturation detection current indicating a saturation of the first gain bipolar transistor.

Abstract: Doherty power amplifiers with a controllable capacitor are disclosed. In certain embodiments, a Doherty power amplifier includes a carrier amplifier that amplifies a first radio frequency (RF) input signal, a peaking amplifier that amplifies a second RF input signal, and a combiner having a first input coupled to an output of the carrier amplifier, a second input coupled to an output of the peaking amplifier, and an output that provides a combined RF output signal. The combiner includes an inverter for providing impedance inversion between the first input and the output of the combiner, and a first controllable capacitor and a first inductor in series and operable to provide harmonic termination to the output of the carrier amplifier. A capacitance of the first controllable capacitor is controllable to tune both the inverter and the harmonic termination of the carrier amplifier.

Abstract: Methods related to power amplification systems with adjustable common base bias. A method of implementing a power amplification system can include providing a cascode amplifier coupled to a radio-frequency input signal and coupled to a radio-frequency output. The method can further include providing 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.

Abstract: Systems and methods including variable power amplifier bias impedance are disclosed. In one aspect, there is provided a power amplifier system including a bias circuit configured to receive a bias voltage and generate a bias signal and a power amplifier stage configured to receive an input radio frequency (RF) signal and generate an output RF signal. The power amplifier system may also include a bias impedance component operatively coupled between the bias circuit and the power amplifier stage. The bias impedance is component configured to receive a control signal and adjust an impedance value of the bias impedance component in response to the control signal.

Abstract: Apparatus and methods for saturation detection of power amplifiers are provided. In certain embodiments, a power amplifier system including a power amplifier and a saturation detector is provided. The power amplifier includes a gain transistor that amplifies an RF input signal to generate an RF output signal, and the saturation detector includes a detection transistor that is thermally coupled to the gain transistor. Additionally, the saturation detector monitors an input voltage to the gain transistor to generate a saturation detection signal indicating a saturation of the gain transistor.

Abstract: The invention provides a differential power amplification stage comprising a first amplification unit adapted to amplify a first differential signal and to output an amplified first differential signal, a second amplification unit adapted to amplify a second differential signal having opposite phase to the first differential signal and to output an amplified second differential signal, and a saturation detection unit adapted to detect gain saturation of the first and second amplification unit, to generate a saturation detection signal indicating the gain saturation of first and second amplification unit, and to provide a virtual ground for the first and second differential signals for RF cancellation on the first and second differential signals. The virtual ground principle is also applied to a Doherty power amplifier module which comprises a saturation detection unit for detecting saturation in the carrier amplification stage.

Abstract: Systems and methods including variable power amplifier bias impedance are disclosed. In one aspect, there is provided a power amplifier system including a bias circuit configured to receive a bias voltage and generate a bias signal and a power amplifier stage configured to receive an input radio frequency (RF) signal and generate an output RF signal. The power amplifier system may also include a bias impedance component operatively coupled between the bias circuit and the power amplifier stage. The bias impedance is component configured to receive a control signal and adjust an impedance value of the bias impedance component in response to the control signal.

Abstract: In some embodiments, a power amplifier circuit can include a power amplifier having an input node and an output node, a load modulation circuit coupled to the output node of the power amplifier, and a phase compensation circuit implemented in the input node side of the power amplifier. The power amplifier circuit can further include a control circuit configured to provide a control signal to the load modulation circuit based on a first current representative of a tunable reference current and a second current representative of a saturation detection current. In some embodiments, the control circuit can be further configured to provide a control signal to the phase compensation circuit based on a third current representative of a tunable reference current and the second current.

Abstract: In some embodiments, a power amplification system can comprise a current source, an input switch configured to alternatively feed current from the current source to a high-power circuit path and a low-power circuit path, and a band switch including a switch arm for switching between a plurality of bands. Each of the high-power circuit path and the low-power circuit path can be connected to the switch arm.

Abstract: The present disclosure relates to devices and methods for detecting and preventing occurrence of a saturation state in a power amplifier. A power amplifier module can include a power amplifier including a cascode transistor pair. The cascode transistor pair can include a first transistor and a second transistor. The power amplifier module can include a current comparator configured to compare a first base current of the first transistor and a second base current of the second transistor to obtain a comparison value. The power amplifier module can include a saturation controller configured to supply a reference signal to an impedance matching network based on the comparison value. The impedance matching network can be configured to modify a load impedance of a load line in electrical communication with the power amplifier based at least in part on the reference signal.

Abstract: In some embodiments, a power amplifier circuit can include a power amplifier having an input node and an output node, and a load modulation circuit coupled to the output node of the power amplifier. The power amplifier circuit can further include a control profile configured to provide information for generating a control signal for the load modulation circuit, and a control circuit configured to generate and provide the control signal to the load modulation circuit based on the control profile. In some embodiments, the control profile can be further configured to provide information for generating a control signal for a phase compensation circuit.

Abstract: In some embodiments, an amplifier circuit can be configured to amplify a radio-frequency signal and include an input stage and an output stage coupled to the input stage and having an output node. The amplifier circuit can further include a load modulation circuit coupled to the output node of the output stage and configured to provide variable capacitance that depends on a control voltage. In some embodiments, the amplifier circuit can be implemented as a power amplifier circuit.

Abstract: Circuits and devices related to radio-frequency amplifiers. In some embodiments, a radio-frequency amplifier can include a plurality of narrow band power amplifiers. Each narrow band power amplifier can be configured to operate with a high voltage in an average power tracking mode and be capable of being coupled to an output filter associated with a respective individual frequency band. Each narrow band power amplifier can be sized smaller than a wide band power amplifier configured to operate with more than one of the frequency bands associated with the plurality of narrow band power amplifiers.

Abstract: Methods related to power amplification systems with adjustable common base bias. A method of implementing a power amplification system can include providing a cascode amplifier coupled to a radio-frequency input signal and coupled to a radio-frequency output. The method can further include providing 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.

Abstract: According to some implementations, a radio-frequency (RF) device includes a communication interface coupled to a serial bus. The RF device also includes a monitoring component coupled to the communication interface, the monitoring component configured to monitor the serial bus for first data transmitted to a first device coupled to the serial bus and configure the RF device based on the first data.

Abstract: In some embodiments, an amplifier system can include an amplifier circuit having first and second amplifiers configured to amplify respective first and second portions of an input signal. Each of the first and second amplifiers can include a cascode stage with input and output transistors arranged in a cascode configuration. The amplifier system can further include an envelope tracking bias circuit coupled to the amplifier circuit and configured to provide a bias signal to the output transistor of the cascode stage of at least one of the first and second amplifiers. The amplifier system can further include a supply circuit configured to provide a non-envelope tracking supply voltage to the output transistor of the cascode stage of the at least one of the first and second amplifiers.

Abstract: Circuits, devices and methods related to antenna tuner. In some embodiments, an antenna can be tuned by amplifying a signal for transmission by operating a transistor with a base current, and monitoring the base current. The method can further include adjusting an antenna tuner to thereby adjust an antenna load impedance presented to the amplified signal, with the adjustment being based on a variation of the monitored base current.

Abstract: According to at least one example of the disclosure, a power amplifier system is provided comprising an amplifying transistor configured to amplify a radio frequency signal, a bias circuit configured to provide a bias voltage to the amplifying transistor, and a clamp circuit for protecting the power amplifier system by absorbing a current flowing through the amplifying transistor when the clamp circuit is switched on. The clamp circuit is connected at a bias node between the bias circuit and the amplifying transistor and includes a clamp transistor and a clamp diode, the clamp diode having one end connected to a collector of the clamp transistor at the bias node and another end connected to a base of the clamp transistor.

Abstract: Apparatus and methods for power amplifier bias modulation for low bandwidth envelope tracking are provided herein. In certain embodiments, a power amplifier system for a mobile device includes a power amplifier that amplifies an RF signal and a low bandwidth envelope tracker that generates a power amplifier supply voltage for the power amplifier based on an envelope of the RF signal. The envelope tracking system further includes a bias modulation circuit that modulates a bias signal of the power amplifier based on a voltage level of the power amplifier supply voltage.

Abstract: The present disclosure relates to devices and methods for detecting and preventing occurrence of a saturation state in a power amplifier. A power amplifier module can include a power amplifier including a cascode transistor pair. The cascode transistor pair can include a first transistor and a second transistor. The power amplifier module can include a current comparator configured to compare a first base current of the first transistor and a second base current of the second transistor to obtain a comparison value. The power amplifier module can include a saturation controller configured to supply a reference signal to an impedance matching network based on the comparison value. The impedance matching network can be configured to modify a load impedance of a load line in electrical communication with the power amplifier based at least in part on the reference signal.