A compensation circuit includes a power amplifier, a current bias circuit, a power detection circuit and a current control circuit; the power detection circuit is configured to detect the voltage amplitude of the radio frequency input signal of the power amplifier and output a reference current when the voltage amplitude meets a preset condition; the current control circuit is configured to receive a reference current and output a compensation current to the current bias circuit based on the reference current; the current bias circuit is configured to receive the compensation current and generate the direct-current bias current, and output the compensation current and the direct-current bias current to the power amplifier; and the power amplifier is configured to receive the compensation current and the direct-current bias current, and amplify the power of the radio frequency input signal based on the compensation current and the direct-current bias current.

The present disclosure relates to a transmitter system that includes a radio frequency (RF) power amplifier (PA) and a baseband processor. The RF PA is configured to amplify an RF input signal to an RF output signal and configured to receive an analog bias adjustment signal, which is applied to correct dynamic bias errors in the RF PA caused by amplification variations that have time constants. The baseband processor, in response to an input envelope and a feedback output envelope, is configured to generate a feedback envelope error signal. Herein, the input envelope is estimated based on a baseband input signal received by the baseband processor, and the feedback output envelope is estimated based on the RF output signal. The RF input signal and the analog bias adjustment signal fed to the RF PA are generated from the baseband input signal and the feedback envelope error signal, respectively.

A system for adapting the voltage of a drain of a power stage includes at least two transmission paths T.sub.Xa, a transmission path comprising a resistive element (1.sub.n), a phase control module (2.sub.n), and a power stage (3.sub.n) at the output of which a radiating element (E.sub.n) is arranged, comprising at least: a device (5.sub.n) for determining the value of a reflected power P.sub.r, the value of an incident power P.sub.i in a power stage, and the ratio of the powers R, an analogue device (6.sub.n) configured so as to pulse width-modulate the difference signal, a switching cell (7.sub.n) receiving a low-power PWM signal and designed to generate a power signal PWM.sub.a that is transformed, by a low-pass filter (8.sub.n), into a bias signal for biasing the power stage in accordance with a predefined bias control law.

Systems and circuits include an amplifier having an output; a switching circuit coupled to the output of the amplifier to provide a bias current to bias the amplifier; first current generating circuitry coupled to the switching circuit; and second current generating circuitry coupled to the output of the amplifier and to the switching circuit. In operation, the switching circuit provides the bias current, during a first time period, in response to a first signal generated by the first current generating circuitry, and provides the bias current, during a second time period, after the first time period, in response to a second signal generated by the second current generating circuitry.

Doherty radio frequency (RF) amplifier circuitry includes an input node, an output node, a main amplifier path, and a peaking amplifier path. The main amplifier path is coupled between the input node and the output node and includes a main amplifier. The peaking amplifier path is coupled in parallel with the main amplifier path between the input node and the output node, and includes a peaking amplifier and a peaking variable gain preamplifier between the input node and the peaking amplifier. The peaking variable gain preamplifier is configured to adjust a current provided to the peaking amplifier.

Techniques for biasing output transistor of a push-pull amplifier output stage are provided. In certain applications the techniques can improve efficiency of the amplifier. In an example, a circuit can include an output stage including first and second output transistors, a first scaled replica transistor corresponding to the first output transistor, and an amplifier circuit in a feedback arrangement for biasing a gate of the first output transistor at a level that, at a specified stand-by current level of the first output transistor, reproduces a voltage difference between the drain and source terminals of the first output transistor across the drain and source terminals of the first replica transistor.

A circuit includes first and second gain stages and an output transistor. The second gain stage includes a transconductance amplifier and a variable impedance circuit coupled to an output of the transconductance amplifier. The variable impedance circuit is configured to implement a first impedance level at frequencies below a first frequency threshold and to implement a second impedance level at frequencies above a second frequency level. The first impedance level is larger than the second impedance level. The output transistor has a control input coupled to the variable impedance circuit. At frequencies above the second frequency threshold, the second impedance level is configured to be inversely related to current through the output transistor.

Apparatus including a first transmission line for transmitting radio frequency, RF, signals and at least one RF device including at least one active semiconductor device for processing RF signals, wherein said at least one RF device is coupled to said first transmission line, and wherein said first transmission line includes an electro-chromic, EC, material a permittivity of which can be controlled by applying a first control voltage to said first transmission line.

A power amplifier device includes: a first power supply terminal for inputting a first power supply voltage; a first transistor for power amplification that (i) includes a first gate to which a bias voltage is applied, and (ii) is supplied with power from the first power supply terminal; a second power supply terminal for inputting a second power supply voltage lower than the first power supply voltage; a second transistor for monitoring that (i) includes a second gate to which the bias voltage is applied, (ii) is supplied with power from the first power supply terminal or the second power supply terminal, and (iii) imitates an operation of the first transistor; and a bias circuit that is supplied with power from the second power supply terminal and generates and adjusts the bias voltage according to a drain current or a source current of the second transistor.

A power amplifier includes an over-current protection loop and/or an over-voltage protection loop to assist in preventing operation outside a safe operation zone. In a further exemplary aspect, triggering of the over-current protection loop adjusts a threshold voltage for the over-voltage protection loop. In further exemplary aspects, the over-current protection loop may adjust not only a bias regulator, but also provide an auxiliary control signal that further limits signals reaching the power amplifier. In still further exemplary aspects, the over-voltage protection loop may operate independently of the over-current protection current loop or the over-voltage protection loop contribute to an over-current protection signal.