A Doherty amplifier is configured in such a way that a phase adjustment circuit adjusts either the phase of a return signal going to a first auxiliary amplification element as a result of passage of a first signal amplified by a second main amplification element through a second auxiliary amplification element as the return signal, or the phase of the return signal going to the second auxiliary amplification element as a result of reflection of the return signal by the first auxiliary amplification element, at a time of a backoff operation of the second auxiliary amplification element, in such a way that the sum of the phase of the return signal going to the first auxiliary amplification element and the phase of the return signal going to the second auxiliary amplification element is not equal to 0 degrees in the operating frequency band of the first signal.

In a preamplifier (amplifier) for the radiation detector, an interconnection layer connected to the bonding pad forms one electrode of a feedback capacitor. Since there is no wiring for connecting the bonding pad and capacitor, a parasitic capacitance caused by the wiring will not be generated. Moreover, the capacitor is arranged below the bonding pad with a conductive layer serving as the other electrode, so that the feedback capacitance of the capacitor is included in the parasitic capacitance between the interconnection layer and the substrate. Compared to the conventional case, an amount of capacitance corresponding to the parasitic capacitance caused by wiring and the feedback capacitance for the capacitor is reduced from the input capacitance. Thus, the input capacitance for the amplifying circuit is reduced.

A biased-transistor-module comprising: a module-input-terminal; a module-output-terminal; a reference-terminal; a module-supply-terminal configured to receive a supply voltage; a module-reference-voltage-terminal configured to receive a module reference voltage; a main-transistor having a main-control-terminal, a main-first-conduction-channel-terminal and a main-second-conduction-channel-terminal, wherein the main-first-conduction-channel-terminal is connected to the module-output-terminal, and the main-second-conduction-channel-terminal is connected to the reference-terminal, and the main-control-terminal is connected to an input-signal-node, wherein the input-signal-node is connected to the module-input-terminal; and a bias-circuit. The bias-circuit comprises: a first-bias-transistor; a first-bias-resistor; a second-bias-transistor; and a second-bias-resistor.

Provided is a bias circuit that supplies a first bias current or voltage to an amplifier that amplifies a radio frequency signal. The bias circuit includes: an FET that has a power supply voltage supplied to a drain thereof and that outputs the first bias current or voltage from a source thereof; a first bipolar transistor that has a collector thereof connected to a gate of the FET, that has a base thereof connected to the source of the FET, that has a common emitter and that has a constant current supplied to the collector thereof; and a first capacitor that has one end thereof connected to the collector of the first bipolar transistor and that suppresses variations in a collector voltage of the first bipolar transistor.

An embodiment of a Doherty amplifier module includes a substrate, an RF signal splitter, a carrier amplifier die, and a peaking amplifier die. The RF signal splitter divides an input RF signal into first and second input RF signals, and conveys the first and second input RF signals to first and second splitter output terminals. The carrier amplifier die includes one or more first power transistors configured to amplify, along a carrier signal path, the first input RF signal to produce an amplified first RF signal. The peaking amplifier die includes one or more second power transistors configured to amplify, along a peaking signal path, the second input RF signal to produce an amplified second RF signal. The carrier and peaking amplifier die are coupled to the substrate so that the RF signal paths through the carrier and peaking amplifier die extend in substantially different (e.g., orthogonal) directions.

When a signal source sends a radio-frequency signal to an input amplification circuit, a control circuit sends a first control signal to the input amplification circuit according to the frequency of the radio-frequency signal, the input amplification circuit receives the first control signal and forms an input oscillation loop, the radio-frequency signal forms an amplified first signal through the input oscillation loop, and the input amplification circuit sends the first signal to the output amplification circuit. According to the frequency of the radio-frequency signal, the control circuit transmits a second control signal to the output amplification circuit, which forms an output oscillation loop matched with the first signal. The first signal is amplified by the output oscillation loop to form an emitting signal, the output amplification circuit transmits the emitting signal to the emitting antenna for emitting, thereby improving the utilization ratio of a radio-frequency front end chip package.

An amplifier circuit is configured in such a way that the amplifier circuit includes: a first amplifier to amplify a signal to be amplified; an output matching circuit through which the signal amplified by the first amplifier propagates; and a second amplifier to amplify the signal which has propagated through the output matching circuit, and the output matching circuit is a lumped constant circuit including multiple lumped constant elements, and, by using the multiple lumped constant elements, transforms the impedance seen on the second amplifier side from the first amplifier when the output power of the second amplifier is lower than saturation electric power, to impedance higher than impedance seen on the second amplifier side from the first amplifier when the output power of the second amplifier is equal to the saturation electric power.

Envelope tracking power amplifiers with advanced gain shaping are provided. In certain implementations, a power amplifier system includes a power amplifier that amplifies a radio frequency (RF) signal and an envelope tracker that controls a voltage level of a supply voltage of the power amplifier based on an envelope of the RF signal. The power amplifier system further includes a gain shaping circuit that generates a gain shaping current that changes with the voltage level of the supply voltage from the envelope tracker. For example, the gain shaping circuit can include an analog look-up table (LUT) mapping a particular voltage level of the supply voltage to a particular current level of gain shaping current. Additionally, the gain shaping circuit biases the power amplifier based on the gain shaping current.

A power amplifier circuit includes a first transistor having a first terminal to which a voltage corresponding to a variable power supply voltage is to be supplied and a second terminal to which a radio-frequency signal is to be supplied, the first transistor being configured to amplify the radio-frequency signal, a bias circuit configured to supply a bias current or voltage to the second terminal of the first transistor, and an adjustment circuit configured to adjust the bias current or voltage in accordance with the variable power supply voltage supplied from a power supply terminal.

A power amplifier circuit includes a first transistor having an emitter electrically connected to a common potential, a base to which a first high-frequency signal is input, and a collector from which a third high-frequency signal is output; a second transistor having an emitter electrically connected to the common potential, a base to which a second high-frequency signal is input, and a collector from which a fourth high-frequency signal is output; a first capacitance circuit electrically connected between the collector of the second transistor and the base of the first transistor; and a second capacitance circuit electrically connected between the collector of the first transistor and the base of the second transistor.