A power amplification circuit includes an amplification transistor, a variable voltage power supply that supplies a variable voltage to a collector of the amplification transistor, a bias circuit that has a constant current amplification transistor outputting a DC bias current to a base of the amplifier transistor, and a current limiting circuit that limits the DC bias current. The current limiting circuit includes a current limiting transistor, a resistor element connected to a collector of the current limiting transistor and the variable voltage power supply, and a resistor element connected to a base of the current limiting transistor and a base of the constant current amplifying transistor.

This application relates to methods and apparatus for amplification of audio signals with improved audio performance. An audio driving circuit has an amplifier module in a forward signal path between an input for receiving an input audio signal (S.sub.IN) and an output for outputting an audio driving signal (V.sub.OUT). A pre-distortion module is operable to apply a first transfer function to the signal in the forward signal path upstream of the amplifier module, wherein the first transfer function comprises a non-linear distortion function based on at least one distortion setting. An error block is arranged to receive a first signal (S.sub.FF) derived from the input signal and a second signal (S.sub.FB) indicative of the voltage of the audio driving signal and determine a first error signal (.sub.1) indicative of a difference between the first and second signals. The pre-distortion module is operable to control the distortion setting(s) based on the first error signal.

An envelope tracking (ET) circuit is provided. In the ET circuit, a number of amplifier circuits are configured to amplify a radio frequency (RF) signal simultaneously to generate multiple RF transmit signals for transmission in a formed RF beam. The RF signal is pre-modulated into respective phase and amplitude terms such that the multiple RF transmit signals can be linearly combined at a receiver(s). A signal processing circuit is configured to determine a combined distortion term in the multiple RF transmit signals. Accordingly, the signal processing circuit pre-distorts the RF signal with a distortion correction term to offset the combined distortion term in the RF transmit signals. By introducing the distortion correction term in the RF signal, it is possible to restore linear coherency among the RF transmit signals without compromising efficiency and/or increasing heat dissipation of the amplifier array(s).

A multimode voltage tracker circuit is provided. The multimode voltage tracker circuit is configured to generate a modulated voltage for amplifying a radio frequency (RF) signal(s), which may be modulated in a wide range of modulation bandwidth. In one non-limiting example, the multimode voltage tracker circuit can be configured to operate in a low modulation bandwidth (LMB) mode to generate an average power tracking (APT) modulated voltage for amplifying the RF signal(s) when the RF signal(s) is modulated in a lower modulation bandwidth (e.g., <50 KHz). As such, the multimode voltage tracker circuit can be adapted to support lower bandwidth communications in an Internet-of-Things (IoT) network with improved efficiency, stability, and performance.

An envelope tracking device includes circuitry that senses a current of an input state of the envelope tracking device. The circuitry also senses an output voltage of the envelope tracking device, and turns on at least one of a first and a second output switches to generate an output current based on at least one of the sensed current and the sensed voltage.

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.

In one aspect the embodiments relate to amplifier circuitry comprising an outphasing region and envelope tracking region. The outphasing region includes a signal processing block capable of receiving an amplitude and phase modulated input signal that is to be amplified, and processing said signal to separate it into two signals (S1, S2) of constant amplitude and modulated phase, a first signal S1 for driving a first RF power amplifier RF PA1 and a second signal S2 for driving a second RF power amplifier RF PA2. The output signals from each of the RF PAs are then provided to a power combiner (PC) for obtaining an output amplified signal (RF output). The envelope tracking region (100b) includes a linear amplifier (Env Amp) capable of receiving an input representing an envelope of the input signal that to be amplified, a charge storage device C1 coupled to said amplifier for providing an amplified envelope signal for driving the RF PAs, said amplifier (8) and charge storage device C1 being arranged to receive a supply voltage V+. The amplifier circuitry is configured such that when the first signal S1 and the second signal S2 in the outphasing circuit 100a are in phase, an input voltage V1 based on the voltage of the received envelope signal is provided to the amplifier in the envelope tracking region to enable the charge storage device C1 to supply a voltage V2 above the supply voltage V+ such that the output voltage of the RF PAs driven by the amplifier (8) is increased by V2 above the supply voltage V+.

A method for controlling a supply voltage of a power amplifier, and an electronic device are provided. The method includes acquiring a state of an envelope of a to-be-amplified signal, where the state of the envelope includes a rising edge and a falling edge; acquiring a first voltage corresponding to the envelope when the state of the envelope is the falling edge, and controlling the supply voltage of the power amplifier according to the first voltage. The method also includes acquiring a second voltage corresponding to a maximum peak value of the to-be-amplified signal in a first preset time when the state of the envelope is the rising edge, and controlling, according to the second voltage, the supply voltage of the power amplifier in the first preset time.

A power amplifier apparatus, includes an envelope tracking (ET) current bias circuit configured to generate a first ET bias current by calculating a direct current DC, based on a reference voltage, and an ET current, based on an ET voltage, according to an envelope of an input signal; and a power amplifier circuit having a bipolar junction transistor supplied with the first ET bias current and a power voltage to amplify the input signal, wherein an average current of the first ET bias current is controlled to be substantially constant.

An envelope tracking (ET) power management circuit is provided. The ET power management circuit includes an amplifier circuit(s) configured to output a radio frequency (RF) signal at a defined power level corresponding to a direct current, an alternating current, and an ET modulated voltage received by the amplifier circuit(s). The ET power management circuit can operate in a high-power ET mode when the defined power level exceeds a defined power level threshold and the RF signal is modulated to include no more than a defined number of resource blocks. The ET power management includes two ET tracker circuitries each generating a respective ET modulated voltage and two charge pump circuitries each generating a respective current. In the high-power ET mode, both charge pump circuitries are activated to each provide a reduced current to the amplifier circuit, thus helping to reduce a footprint and cost of the ET power management circuit.