An RF amplifier circuit includes an amplifier and a feedback circuit. The feedback circuit includes a resistive feedback circuit coupled between an input and output of the amplifier and a shunt feedback circuit coupled between the output of the amplifier and a reference input. The resistive feedback circuit includes a first set of serially coupled resistors and a first set of switches. The first sets of resistors and switches are arranged in a ladder structure with each switch of the first set of switches configured to bypass one of the resistors of the first set of resistors. The shunt feedback circuit includes a second set of serially coupled resistors and a second set of switches. The second sets of resistors and switches are arranged in a ladder structure with each switch of the second set of switches configured to bypass one of the resistors of the second set of resistors.

An RF amplifier circuit includes an amplifier and a feedback circuit. The feedback circuit includes a resistive feedback circuit coupled between an input and output of the amplifier and a shunt feedback circuit coupled between the output of the amplifier and a reference input. The resistive feedback circuit includes a first set of serially coupled resistors and a first set of switches. The first sets of resistors and switches are arranged in a ladder structure with each switch of the first set of switches configured to bypass one of the resistors of the first set of resistors. The shunt feedback circuit includes a second set of serially coupled resistors and a second set of switches. The second sets of resistors and switches are arranged in a ladder structure with each switch of the second set of switches configured to bypass one of the resistors of the second set of resistors.

A low-noise amplifier in a receiver supporting a beam forming function may selectively change a phase shift for beam steering. The low-noise amplifier may include first and second transistors and a variable capacitance circuit connected to a gate of the second transistor. The variable capacitance circuit may selectively change capacitance thereof based on a capacitance control signal applied thereto according to beam-forming information, where the changed capacitance correspondingly causes a phase change in an output signal of the low-noise amplifier. A similar scheme may be employed for amplifiers in transmit signal paths to steer a transmit beam.

A low-noise amplifier in a receiver supporting a beam forming function may selectively change a phase shift for beam steering. The low-noise amplifier may include first and second transistors and a variable capacitance circuit connected to a gate of the second transistor. The variable capacitance circuit may selectively change capacitance thereof based on a capacitance control signal applied thereto according to beam-forming information, where the changed capacitance correspondingly causes a phase change in an output signal of the low-noise amplifier. A similar scheme may be employed for amplifiers in transmit signal paths to steer a transmit beam.

A compound semiconductor device includes: a semiconductor laminate structure including an electron transit layer and an electron supply layer that are formed from a compound semiconductor; a gate electrode, a source electrode, and a drain electrode that are provided above the electron supply layer; and an insulating layer that is provided between the source electrode and the drain electrode, over the semiconductor laminate structure, and with a gate recess formed therein, wherein the gate electrode includes: a first portion in the gate recess; and a second portion that is coupled to the first portion and is provided over the insulating layer at a position further on the drain electrode side than the gate recess, wherein the insulating layer includes an aluminum oxide film in direct contact with the semiconductor laminate structure.

A compound semiconductor device includes: a semiconductor laminate structure including an electron transit layer and an electron supply layer that are formed from a compound semiconductor; a gate electrode, a source electrode, and a drain electrode that are provided above the electron supply layer; and an insulating layer that is provided between the source electrode and the drain electrode, over the semiconductor laminate structure, and with a gate recess formed therein, wherein the gate electrode includes: a first portion in the gate recess; and a second portion that is coupled to the first portion and is provided over the insulating layer at a position further on the drain electrode side than the gate recess, wherein the insulating layer includes an aluminum oxide film in direct contact with the semiconductor laminate structure.

An envelope tracking power amplifier module and an envelope tracking method are provided. The envelope tracking power amplifier module includes a power amplifier and a linear amplifier coupled to the power amplifier and configured to receive and amplify an envelope signal and provide the amplified envelope signal to the power amplifier. The power amplifier is configured to receive and amplify a signal according to the amplified envelope signal. The envelope tracking method includes: providing a signal to the power amplifier; deriving an envelope phase of the signal, the envelope phase corresponding to an output power of the power amplifier; providing an envelope signal including the envelope phase to the envelope tracking module; the envelope tracking module providing the amplified envelope signal to the power amplifier; and the power amplifier amplifying the signal according to the amplified envelope signal and outputting the amplified signal at the output power.

A multi-level charge pump (MCP) circuit is provided. The MCP circuit includes a multi-level voltage circuit configured to receive a supply voltage and generate a low-frequency voltage. The multi-level voltage circuit includes a first switch path, a second switch path, and a third switch path each having a respective on-resistance and coupled in parallel between an input node and an output node. In a non-limiting example, the multi-level voltage circuit is configured to activate the first switch path and at least one of the second switch path and the third switch path when the multi-level voltage circuit generates the low-frequency voltage that equals the supply voltage. By activating at least two of the three switch paths to generate the low-frequency voltage, it may be possible to reduce an equivalent resistance of the multi-level voltage circuit, thus helping to improve efficiency and reduce power loss of the MCP circuit.

High frequency amplifier circuitry includes a common-source first transistor to amplify a high-frequency input signal, a common-gate second transistor cascade-connected to the first transistor, to amplify a signal amplified by the first transistor to generate an output signal, a first inductor connected between a source of the first transistor and a first reference potential node, a second inductor connected between a drain of the second transistor and a second reference potential node, and non-linear compensation circuitry connected to a connection node of the first transistor and the second transistor, to compensate for non-linearity of the output signal to the high-frequency input signal. The non-linear compensation circuitry has first rectifier circuitry, a first resistor, a second resistor, second rectifier circuitry, first capacitor and second capacitor.

High frequency amplifier circuitry includes a common-source first transistor to amplify a high-frequency input signal, a common-gate second transistor cascade-connected to the first transistor, to amplify a signal amplified by the first transistor to generate an output signal, a first inductor connected between a source of the first transistor and a first reference potential node, a second inductor connected between a drain of the second transistor and a second reference potential node, and non-linear compensation circuitry connected to a connection node of the first transistor and the second transistor, to compensate for non-linearity of the output signal to the high-frequency input signal. The non-linear compensation circuitry has first rectifier circuitry, a first resistor, a second resistor, second rectifier circuitry, first capacitor and second capacitor.