A power amplifier circuit includes a first transistor that amplifies an RF signal; a bias current source that supplies a bias current to a second terminal of the first transistor through a first current path; and an adjustment circuit that adjusts the bias current in accordance with a variable power-supply voltage supplied from a power-supply terminal. The adjustment circuit includes first to third resistors, and an adjustment transistor including a first terminal connected to the power-supply terminal through the first resistor, a second terminal connected to the bias current source through the second resistor, and a third terminal connected to the first current path through the third resistor. When the variable power-supply voltage is not less than a first voltage and not greater than a third voltage, the adjustment circuit increases a current that flows to the power-supply terminal through a second current path as the variable power-supply voltage decreases.

Power amplification system with variable supply voltage. A power amplification system can include a power amplifier and a boost converter configured to provide a supply voltage to the power amplifier. The power amplification system can include a control system configured to provide a boost converter control signal to the boost converter to adjust the supply voltage based on a parameter associated with the power amplifier.

Power amplification system with variable supply voltage. A power amplification system can include a power amplifier and a boost converter configured to provide a supply voltage to the power amplifier. The power amplification system can include a control system configured to provide a boost converter control signal to the boost converter to adjust the supply voltage based on a parameter associated with the power amplifier.

Provided is a power amplification module that includes: a first amplification circuit that amplifies a first signal and outputs the amplified first signal as a second signal; a second amplification circuit that amplifies the second signal and outputs the amplified second signal as a third signal; and a feedback circuit that re-inputs/feeds back the second signal outputted from the first amplification circuit to the first amplification circuit as the first signal. The operation of the first amplification circuit is halted and the first signal passes through the feedback circuit and is outputted as the second signal at the time of a low power output mode.

Provided is a power amplification module that includes: a first amplification circuit that amplifies a first signal and outputs the amplified first signal as a second signal; a second amplification circuit that amplifies the second signal and outputs the amplified second signal as a third signal; and a feedback circuit that re-inputs/feeds back the second signal outputted from the first amplification circuit to the first amplification circuit as the first signal. The operation of the first amplification circuit is halted and the first signal passes through the feedback circuit and is outputted as the second signal at the time of a low power output mode.

In some embodiments, a power amplification system can comprise a current source, an input switch configured to alternatively feed current from the current source to a high-power circuit path and a low-power circuit path, and a band switch including a switch arm for switching between a plurality of bands. Each of the high-power circuit path and the low-power circuit path can be connected to the switch arm.

A power amplifying circuit includes a first amplifying unit that amplifies a first radio-frequency signal and a second amplifying unit that amplifies a second radio-frequency signal. The first amplifying unit includes a first matching circuit that performs impedance matching for a circuit in a preceding stage, and a first amplifying circuit that amplifies the first radio-frequency signal that has passed through the first matching circuit. The second amplifying unit includes a second matching circuit that performs impedance matching for the circuit in the preceding stage, a resistor including a first end and a second end, the first end being electrically connected to the second matching circuit, and a second amplifying circuit that is electrically connected to the second end of the resistor and that amplifies the second radio-frequency signal that has passed through the resistor.

The disclosure provides an amplifier. The amplifier includes a first transistor that receives a first input and generates a first load current. A first output node is coupled to a power supply through a first load resistor. The first load resistor receives the first load current. A first capacitor network is coupled to the first output node and draws a first capacitive current from the first output node. A first current buffer is coupled between the first output node and the first transistor. A current through the first current buffer is a summation of the first load current and the first capacitive current.

The disclosure provides an amplifier. The amplifier includes a first transistor that receives a first input and generates a first load current. A first output node is coupled to a power supply through a first load resistor. The first load resistor receives the first load current. A first capacitor network is coupled to the first output node and draws a first capacitive current from the first output node. A first current buffer is coupled between the first output node and the first transistor. A current through the first current buffer is a summation of the first load current and the first capacitive current.

Power amplification system with adjustable common base bias. A power amplification system can include a cascode amplifier coupled to a radio-frequency input signal and coupled to a radio-frequency output. The power amplification system can further include a biasing component configured to apply one or more biasing signals to the cascode amplifier, the biasing component including a bias controller and one or more bias components. Each respective bias component may be coupled to a respective bias transistor.