A power amplifier includes an amplifying circuit, including an amplifying transistor configured to amplify an input signal and configured to output an output signal, a bias circuit, including a bias transistor comprising an emitter configured to provide a bias current into a base of the amplifying transistor, and a base into which a control current is input, and an overcurrent protecting circuit configured to bypass the control current into a ground, according to a current level of the output signal.

A power amplifier module includes an amplifier transistor and a bias circuit. A first power supply voltage based on a first operation mode or a second power supply voltage based on a second operation mode is supplied to the amplifier transistor. The amplifier transistor receives a first signal and outputs a second signal obtained by amplifying the first signal. The bias circuit supplies a bias current to the amplifier transistor. The bias circuit includes first and second resistors and first and second transistors. The first transistor is connected in series with the first resistor and is turned ON by a first bias control voltage which is supplied when the first operation mode is used. The second transistor is connected in series with the second resistor and is turned ON by a second bias control voltage which is supplied when the second operation mode is used.

A power amplifier apparatus is provided. The power amplifier apparatus includes a number of multi-stage power amplifiers and a bias circuit configured to generate a number of bias signals (e.g., bias current or bias voltage) to control (e.g., activate or deactivate) the multi-stage power amplifiers. In examples disclosed herein, only one of the multi-stage power amplifiers is activated at a given time. In this regard, the bias circuit can generate the bias signals to collectively activate one of the multi-stage power amplifiers, while deactivating the rest of the multi-stage power amplifiers. As such, it may be possible to control a larger number of power amplifier stages based on a smaller number of bias signals. As a result, it may be possible to eliminate a biasing bump pad(s) from the power amplifier apparatus, thus helping to reduce the footprint and cost of the power amplifier apparatus.

A power amplifier includes an amplifying circuit, including an amplifying transistor configured to amplify an input signal and configured to output an output signal, a bias circuit, including a bias transistor comprising an emitter configured to provide a bias current into a base of the amplifying transistor, and a base into which a control current is input, and an overcurrent protecting circuit configured to bypass the control current into a ground, according to a current level of the output signal.

A first amplifier circuit in a preceding stage, a second amplifier circuit in a subsequent stage, and a ground external connection terminal are disposed on a substrate. The first and second amplifier circuits each include bipolar transistors, capacitive elements for the respective bipolar transistors, and resistive elements for the respective bipolar transistors. The bipolar transistors each include separate base electrodes, that is, a first base electrode for radio frequency and a second base electrode for biasing. The bipolar transistors of the second amplifier circuit include emitter electrodes connected to the ground external connection terminal. The minimum spacing between the first base electrode and an emitter mesa layer of at least one of the bipolar transistors of the second amplifier circuit is greater than the minimum spacing between the first base electrode and am emitter mesa layer of each of the bipolar transistors of the first amplifier circuit.

An amplifier arrangement for amplifying an input signal to an output signal for delivering to a load is disclosed. The amplifier arrangement comprises a power splitter configured to receive the input signal and produce split input signals. The amplifier arrangement further comprises a first amplifier branch comprising multiple main amplifier circuits. Output signals of the multiple main amplifier circuits are combined to generate a first output signal. The amplifier arrangement further comprises a second amplifier branch comprising at least one auxiliary amplifier circuit. The at least one auxiliary amplifier circuit is configured to receive a split input signal from the power splitter and produce a second output signal. The amplifier arrangement further comprises a power combiner configured to receive the first and second output signals and produce the output signal for delivering to the load.

A power amplifier circuit includes a first transistor, wherein a radio frequency signal is inputted to a base or gate of the first transistor; a second transistor having an emitter connected to a collector or drain of the first transistor, wherein a first voltage is supplied to a collector of the second transistor, and a first amplified signal obtained by amplifying the radio frequency signal is outputted from the collector of the second transistor; and a third transistor configured to supply a bias voltage to a base of the second transistor. A second voltage is supplied to a collector or drain of the third transistor, a third voltage corresponding to the first voltage is supplied to a base or gate of the third transistor, and the bias voltage, which corresponds to the third voltage, is supplied from an emitter or source of the third transistor.

A power amplifier module includes an amplifier transistor and a bias circuit. A first power supply voltage based on a first operation mode or a second power supply voltage based on a second operation mode is supplied to the amplifier transistor. The amplifier transistor receives a first signal and outputs a second signal obtained by amplifying the first signal. The bias circuit supplies a bias current to the amplifier transistor. The bias circuit includes first and second resistors and first and second transistors. The first transistor is connected in series with the first resistor and is turned ON by a first bias control voltage which is supplied when the first operation mode is used. The second transistor is connected in series with the second resistor and is turned ON by a second bias control voltage which is supplied when the second operation mode is used.

A multistage power amplifier comprises a first amplification circuit which receives a first bias current; a second amplification circuit which receives a second bias current; an envelope detection circuit which outputs a direct current (DC) detection voltage based on an envelope of an input radio frequency (RF) signal; and a bias compensation circuit which compensates for the first bias current based on the second bias current in response to the DC detection voltage.

A temperature correction circuit and method for maintaining a transistor of a power amplifier in a linear operating region of the transistor. The temperature correction circuit includes a first current source circuit operable to provide a first correction current proportional to an absolute temperature of a semiconductor die including the transistor. The temperature correction circuit also includes a second current source circuit operable to provide a second correction current proportional to a change in temperature of a part of the semiconductor die in which the transistor is located during operation of the transistor. The temperature correction circuit further includes a third current source circuit operable to provide a gain selection current. The temperature correction circuit also includes circuitry for producing a reference current from the first and second correction currents and the gain current. The temperature correction circuit further includes an output for providing the reference current to the transistor.