A digital power amplifier comprising two or more individually activatable amplifiers. The outputs of the amplifiers are connected causing an activated amplifier of the two or more amplifiers to load modulate another activated amplifier of the two or more amplifiers.

A low power radio frequency (RF) signal detector comprising a set of transistors, a bias input circuitry configured to apply bias to each of the set of transistors, and a differential signal input circuitry configured to apply a pair of differential signals to the set of transistors, wherein the pair of differential signals increases or decreases bias applied to the set of transistors to achieve low power, high frequency RF signal detection.

A low power radio frequency (RF) signal detector comprising a set of transistors, a bias input circuitry configured to apply bias to each of the set of transistors, and a differential signal input circuitry configured to apply a pair of differential signals to the set of transistors, wherein the pair of differential signals increases or decreases bias applied to the set of transistors to achieve low power, high frequency RF signal detection.

An amplifier circuit includes: a plurality of amplifiers; a plurality of monitor elements provided for each of the plurality of amplifiers and disposed on a same chip with the corresponding amplifier; and a processor configured to: measure characteristics of each of the plurality of monitor elements; reduce a difference in distortion between a plurality of signals output from the plurality of amplifiers based on the measured characteristics; and compensate for the distortion.

A phase shifter capable of improving phase accuracy by a simple method is provided. The phase shifter includes a hybrid coupler circuit including inductors with mutual inductances, an amplifying circuit, an impedance matching circuit provided between the hybrid coupler circuit and the amplifying circuit. The impedance matching circuit includes a first resistance element connected to an output node of the hybrid coupler circuit, a capacitance element connected between the first resistance element and the ground line in series, another inductor connected in parallel with the first resistance element, and a second resistance element provided between the inductor and the ground line in series.

A semiconductor device is proposed. The semiconductor device includes a group III-N semiconductor layer, an electrically insulating material layer located on the group III-N semiconductor layer, and a metal contact structure located on the electrically insulating material layer. An electrical resistance between the metal contact structure and the group III-N semiconductor layer through the electrically insulating material layer is smaller than 1*10.sup.7 for an area of 1 mm.sup.2. Further, semiconductor devices including a low resistance contact structure, radio frequency devices, and methods for forming semiconductor devices are proposed.

A semiconductor device is proposed. The semiconductor device includes a group III-N semiconductor layer, an electrically insulating material layer located on the group III-N semiconductor layer, and a metal contact structure located on the electrically insulating material layer. An electrical resistance between the metal contact structure and the group III-N semiconductor layer through the electrically insulating material layer is smaller than 1*10.sup.7 for an area of 1 mm.sup.2. Further, semiconductor devices including a low resistance contact structure, radio frequency devices, and methods for forming semiconductor devices are proposed.

Provided is a current output circuit that includes: a first FET that has a power supply voltage supplied to a source thereof, that has a first voltage supplied to a gate thereof and that outputs a first current from a drain thereof; a second FET that has the power supply voltage supplied to a source thereof, that has the first voltage supplied to a gate thereof and that outputs an output current from a drain thereof; a first control circuit that controls the first voltage such that the first current comes to be at a target level; and a second control circuit that performs control such that a drain voltage of the first FET and a drain voltage of the second FET are made equal to each other.

Provided is a current output circuit that includes: a first FET that has a power supply voltage supplied to a source thereof, that has a first voltage supplied to a gate thereof and that outputs a first current from a drain thereof; a second FET that has the power supply voltage supplied to a source thereof, that has the first voltage supplied to a gate thereof and that outputs an output current from a drain thereof; a first control circuit that controls the first voltage such that the first current comes to be at a target level; and a second control circuit that performs control such that a drain voltage of the first FET and a drain voltage of the second FET are made equal to each other.

The invention relates to a resonator circuit, the resonator circuit comprising a transformer comprising a primary winding and a secondary winding, wherein the primary winding is inductively coupled with the secondary winding, a primary capacitor being connected to the primary winding, the primary capacitor and the primary winding forming a primary circuit, and a secondary capacitor being connected to the secondary winding, the secondary capacitor and the secondary winding forming a secondary circuit, wherein the resonator circuit has a common mode resonance frequency at an excitation of the primary circuit in a common mode, wherein the resonator circuit has a differential mode resonance frequency at an excitation of the primary circuit in a differential mode, and wherein the common mode resonance frequency is different from the differential mode resonance frequency.