A bipolar transistor includes a collector layer, a base layer, and an emitter layer that are formed in this order on a compound semiconductor substrate. The emitter layer is disposed inside an edge of the base layer in plan view. A base electrode is disposed on partial regions of the emitter layer and the base layer so as to extend from an inside of the emitter layer to an outside of the base layer in plan view. An insulating film is disposed between the base electrode and a portion of the base layer, with the portion not overlapping the emitter layer. An alloy layer extends from the base electrode through the emitter layer in a thickness direction and reaches the base layer. The alloy layer contains at least one element constituting the base electrode and elements constituting the emitter layer and the base layer.

The invention discloses a dual-mode power amplifier with switchable working power and a mode switch method. The power amplifier adopts a multi-tap input transformer, and realizes the switching between preload line and output load line by controlling the on/off of the intermediate switch connected with taps, so as to achieve the best power conversion efficiency under different maximum output powers. By using the change-over switch to control the capacitance value of the matching capacitor, it is easier to adjust the load line, thus further ensuring the performance of the power amplifier provided by the invention. The intermediate switch and change-over switch are integrated on an independent chip by CMOS/phemt/bihemt/SeGe/SOI, etc, or on a power amplifier chip by CMOS/phemt/bihemt/SeGe/SOI, etc, which is easy to realize.

An amplifier includes an amplifying device and a bias circuit for providing a bias voltage for the amplifying device. The bias circuit is configured to provide the bias voltage in dependence of an output signal of an optical coupling arrangement which provides for electrical isolation.

Apparatus and methods for a no-load-modulation power amplifier are described. No-load-modulation power amplifiers can comprise multiple amplifiers connected in parallel to amplify a signal that has been divided into parallel circuit branches. One of the amplifiers can operate as a main amplifier in a first amplification class and the remaining amplifiers can operate as peaking amplifiers in a second amplification class. The main amplifier can see essentially no modulation of its load between the power amplifier's fully-on and fully backed-off states. The power amplifiers can operate in symmetric and asymmetric modes. Improvements in bandwidth and drain efficiency over conventional Doherty amplifiers are obtained. Further improvements can be obtained by combining signals from the amplifiers with hybrid couplers.

A circuit including an amplifier having an input and an output. The circuit also includes a current-to-voltage amplifier having an input. The circuit further includes a current mirror coupled between the output of the amplifier and the input of the current-to-voltage amplifier. The current mirror is configured to chop current flowing through the first current mirror.

A power amplifier includes a semiconductor die, and an amplifier and bias circuit integrally formed with the semiconductor die. The die has opposed first and second sides, and a device bisection line extends between the first and second sides. The bias circuit includes a multi-point input terminal with first and second terminals that are electrically connected through a conductive path that extends across the device bisection line, and one or more bias circuit components connected between the multi-point input terminal and the amplifier. The amplifier may include a field effect transistor (FET) with gate and drain terminals, and the bias circuit component(s) are electrically connected between the multi-point input terminal and the gate terminal. In addition or alternatively, the bias circuit component(s) are electrically connected between a multi-point input terminal and the drain terminal. The one or more components may include a resistor-divider circuit.

A Doherty amplifier circuit having a tunable impedance and phase (“TIP”) circuit to provide an adjustable alpha factor, which allows for a selection of power added efficiency (PAE) curves that are useful for applications having different modulations or to meet other criteria. Embodiments include a Doherty amplifier having a TIP circuit that provides for tunability of the impedance Z.sub.INV (resulting in an adjustable alpha factor) while maintaining the phase of the output of the carrier amplifier at 90° (for a selected polarity)±a low phase variation. Embodiments of the TIP circuit include one or more series-connected TIP cells comprising at least one TIP circuit combined with a tunable phase adjustment circuit. In operation, when the impedance of a TIP cell is adjusted, adjustments within the cell are also made to provide a phase shift correction back towards 90° (at the selected polarity).

Doherty power amplifier (PA) devices (e.g., packages and modules) including integrated output combining networks are disclosed. In embodiments, the Doherty PA device includes a first amplifier die having a first transistor with a first output terminal at which a first amplified signal is generated, a second amplifier die having a second transistor with a second output terminal at which a second amplified signal is generated, and an output combining network. The output combining network includes, in turn, a combining node integrally formed with the second amplifier die and electrically coupled to the second output terminal. At least one die-to-die bond wire electrically couples the first output terminal to the combining node. The at least one die-to-die bond wire has an electrical length, which is results in a 90 degree phase shift imparted to the first amplified signal between the first output terminal and the combining node.

A packaged RF power amplifier (RFPA) configured to increase video bandwidth is disclosed as well is a process for implementing a RF power device to increase video bandwidth. The RF power device including at least one transistor; an output matching circuit coupled to an output lead and to the at least one transistor; at least one bias feed circuit coupled to the at least one transistor; and at least one coaxial resonator coupled between the at least one transistor and the at least one bias feed circuit.

In one embodiment, an apparatus includes: a digital baseband circuit to receive a digital baseband signal and output a first digital baseband signal and a second digital baseband signal, the second digital baseband signal comprising a scaled version of the first digital baseband signal; a first transmitter signal path coupled to the digital baseband circuit to process the first digital baseband signal and output a first radio frequency (RF) signal; a second transmitter signal path coupled to the digital baseband circuit to process the second digital baseband signal and output a second RF signal; a first power amplifier coupled to the first transmitter signal path to amplify the first RF signal and output an amplified first RF signal; and a second power amplifier coupled to the second transmitter signal path to amplify the second RF signal and output an amplified second RF signal.