An envelope tracking current bias circuit of a power amplifier circuit including a power amplifier includes a first current source circuit configured to generate a first bias current based on a reference voltage, a second current source circuit configured to generate a second bias current based on an envelope voltage of an input signal, and a bias current generator configured to generate a first envelope tracking bias current based on the first bias current and the second bias current, and supply the first envelope tracking bias current to the power amplifier circuit to reduce amplitude modulation-phase modulation (AM-PM) distortion of the power amplifier 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.

Apparatus and methods for envelope tracking systems are provided. In certain configurations, an envelope tracking system includes a digital filter that generates a filtered envelope signal based on a digital envelope signal representing an envelope of a radio frequency signal, a buck converter controllable by the filtered envelope signal and including an output electrically connected to a power amplifier supply voltage, a digital-to-analog converter module including an output electrically connected to the output of the buck converter and that provides an output current, and a digital shaping and delay circuit configured to generate a shaped envelope signal based on shaping the filtered envelope signal. The shaped envelope signal controls a magnitude of the output current, and the digital shaping and delay circuit controls a delay of the shaped envelope signal to align the output of the digital-to-analog converter module and the output of the buck converter.

A power amplifier control method is disclosed. A phase modulation control signal may be generated according to an envelope signal that is output by a baseband unit. The phase modulation may be performed on a signal of a main power amplifier link and/or an auxiliary power amplifier link in the Doherty power amplifier circuit according to the phase modulation control signal, so that a phase difference between the signal of the main power amplifier link and the signal of the auxiliary power amplifier link after the phase modulation is a specified value corresponding to a current value of the envelope signal, where the specified value is an optimal phase value of a Doherty power amplifier circuit when the supply voltage of the Doherty power amplifier circuit is an envelope voltage corresponding to the current value of the envelope signal. High-efficiency power amplifier technology is realized.

A power amplifier module includes a plurality of power amplifiers and at least one switch that switches between power supply sources such that each of the plurality of power amplifiers is supplied with one of a power supply voltage according to an envelope tracking scheme or a power supply voltage according to an average power tracking scheme.

Embodiments of radio frequency (RF) systems include a transmit/receive switch integrated with one or more power amplifiers and/or other components. The power amplifiers can have transformer-based architectures, and a power amplifier and switch can be integrated onto a single complementary metal oxide semiconductor die.

A multi-mode power management circuit is provided. The multi-mode power management circuit includes an unlicensed band amplifier circuit configured to amplify a radio frequency (RF) signal for transmission in an unlicensed RF band(s). In examples described herein, the unlicensed RF band(s) resides in the 5 GHz RF spectrum and is shared between long-term evolution (LTE) enhanced licensed assisted access (eLAA) and Wi-Fi connectivity. In addition, the multi-mode power management circuit can also support LTE communication in a licensed RF band(s). The multi-mode power management circuit can be dynamically and flexibly configured to support a variety of eLAA, Wi-Fi, and LTE communication scenarios (e.g., uplink carrier aggregation) in licensed and/or unlicensed RF band(s) based on such power management schemes as envelope tracking (ET). In this regard, the multi-mode power management circuit can support eLAA, Wi-Fi, and LTE convergence in a mobile device without compromising power management efficiency and/or increasing footprint.

Envelope tracking can be employed to reduce power consumption of a power amplifier, but envelope tracking can introduce nonlinearities to a power amplifier. These nonlinearities can manifest themselves as noise at the output of the power amplifier. Embodiments described herein provide techniques for characterizing a parameter indicative of power amplifier noise when envelope tracking is employed. Measurement of this parameter can permit power amplifier designers to decide whether to forgo envelope tracking if a power amplifier is too susceptible to such noise, redesign the power amplifier to improve compatibility with envelope tracking, or to employ distortion compensation circuitry to reduce the noise output by the power amplifier. Counterintuitively, this distortion compensation circuitry may involve increasing the power, such as the envelope tracking power supply. However, increasing the power may be a desirable trade-off for increased linearity.

Apparatus and methods for reducing inductor ringing of a voltage converter are provided. In certain configurations, a voltage converter includes an inductor connected between a first node and a second node, a plurality of switches, and a bypass circuit having an activated state and a deactivated state. The switches includes a first switch connected between a battery voltage and the first node, a second switch connected between the first node and a ground voltage, a third switch connected between the second node and the ground voltage, and a fourth switch connected between the second node and the output. The bypass circuit includes a first pair of transistors connected between the first node and the second node and configured to turn on to bypass the inductor in the activated state and to turn off in the deactivated state.

Provided is a power amplification module that includes: an amplification transistor that has a constant power supply voltage supplied to a collector thereof, a bias current supplied to a base thereof and that amplifies an input signal input to the base thereof and outputs an amplified signal from the collector thereof; a first current source that outputs a first current that corresponds to a level control voltage that is for controlling a signal level of the amplified signal; and a bias transistor that has the first current supplied to a collector thereof, a bias control voltage connected to a base thereof and that outputs the bias current from an emitter thereof.