Embodiments disclosed herein relate to a bias circuit that uses Schottky diodes. Typically, a bias circuit will include a number of transistors used to generate a bias voltage or a bias current for a power amplifier. Many wireless devices include power amplifiers to facilitate processing signals for transmission and/or received signals. By substituting the bias circuit design with a design that utilizes Schottky diodes, the required battery voltage of the bias circuit may be reduced enabling the use of lower voltage power supplies.

The present disclosure describes a synchronized switching power supply for a radio frequency (RF) power amplifier. In some aspects, a synchronized power supply circuit comprises a first switch connected between a power rail and a first terminal of an inductor that is connected to an output of the circuit via its second terminal. The circuit also includes a second switch connected between a ground rail and the first terminal of the inductor, and respective gate drivers for the first and second switches. An amplifier of the circuit is connected to the power rail and has an output connected to the output of the circuit. A current sensor is connected between the output of the amplifier and the output of the circuit, with an output of the current sensor being connected to an input of a comparator. A delay circuit is connected between an output of the comparator and the first and second gate drivers, and may synchronize the power supply circuit.

Bias circuits and methods for silicon-based amplifier architectures that are tolerant of supply and bias voltage variations, bias current variations, and transistor stack height, and compensate for poor output resistance characteristics. Embodiments include power amplifiers and low-noise amplifiers that utilize a cascode reference circuit to bias the final stages of a cascode amplifier under the control of a closed loop bias control circuit. The closed loop bias control circuit ensures that the current in the cascode reference circuit is approximately equal to a selected multiple of a known current value by adjusting the gate bias voltage to the final stage of the cascode amplifier. The final current through the cascode amplifier is a multiple of the current in the cascode reference circuit, based on a device scaling factor representing the relative sizes of the transistor devices in the cascode amplifier and in the cascode reference circuit.

The present disclosure describes a synchronized switching power supply for a radio frequency (RF) power amplifier. In some aspects, a synchronized power supply circuit comprises a first switch connected between a power rail and a first terminal of an inductor that is connected to an output of the circuit via its second terminal. The circuit also includes a second switch connected between a ground rail and the first terminal of the inductor, and respective gate drivers for the first and second switches. An amplifier of the circuit is connected to the power rail and has an output connected to the output of the circuit. A current sensor is connected between the output of the amplifier and the output of the circuit, with an output of the current sensor being connected to an input of a comparator. A delay circuit is connected between an output of the comparator and the first and second gate drivers, and may synchronize the power supply circuit.

Apparatus and methods for envelope tracking systems with automatic mode selection are provided herein. In certain configurations, a power amplifier system includes a power amplifier that amplifies a radio frequency signal and that receives power from a power amplifier supply voltage. The power amplifier system further includes an envelope tracker that generates the power amplifier supply voltage based on an envelope signal corresponding to an envelope of the radio frequency signal. The envelope tracker includes a signal bandwidth detection circuit that processes the envelope signal to generate a detected bandwidth signal, and a mode control circuit that controls a mode of the error amplifier based on the detected signal bandwidth.

A linearization circuit reduces intermodulation distortion in an amplifier that includes a first stage and a second stage. The linearization circuit receives a first signal that includes a first frequency and a second frequency and generates a difference signal having a frequency approximately equal to the difference of the first frequency and the second frequency, generates an envelope signal based at least in part on a power level of the first signal, and adjusts a magnitude of the difference signal based on the envelope signal. When the amplifier receives the first signal at an input terminal, the first stage receives the adjusted signal, and the second stage does not receive the adjusted signal, intermodulation between the adjusted signal and the first signal cancels at least a portion of the intermodulation between the first frequency and the second frequency from the output of the amplifier.

Provided is a power supply circuit for a wireless mobile device having a plurality of power amplification components. The power supply circuit includes: a first DC-DC converter, for providing at least one constant output voltage (which is provided to the power amplification components) and/or at least one DC intermediate voltage; a second DC-DC converter, for providing a DC component of at least one time-varying output voltage; and at least one linear amplifier. When the at least one linear amplifier receives the at least one DC intermediate voltage from the first DC-DC converter, the at least one linear amplifier provides at least one AC component of the at least one time-varying output voltage. The DC component and the at least one AC component of the at least one time-varying output voltage are combined into the at least one time-varying output voltage and provided to the power amplification components.

Envelope tracking power converter circuitry is configured to receive a supply voltage and simultaneously provide two envelope tracking power supply signals, an envelope tracking power supply signal and an average power tracking power supply signal, or a single envelope tracking power supply signal with improved efficiency. When providing a single envelope tracking power supply signal, an envelope tracking power supply signal is provided to a parallel amplifier in the envelope tracking power converter circuitry to provide multiple levels of envelope tracking which improves efficiency.

The power amplifier circuit includes a first amplifier that amplifies a first signal and outputs a second signal, a second amplifier that amplifies the second signal and outputs a third signal, a power supply terminal that receives supply of a power supply voltage that varies as a function of an amplitude of the first signal, a first power supply line that supplies the power supply voltage from the power supply terminal to the first amplifier, a second power supply line that supplies the power supply voltage from the power supply terminal to the second amplifier, and a first delay circuit provided in the second power supply line.

A method and apparatus is provided. The method includes determining a training data set comprising input and output data of a power amplifier, determining compensation data by regressing the training data using a frequency domain weighting function, storing the compensation data, and linearizing an output of the power amplifier using the stored compensation data.