An amplifier circuit includes a first amplifier that amplifies a high frequency signal, and a load circuit that changes a load impedance of the first amplifier without being controlled by an external circuit so that a saturation power at a first temperature is higher than a saturation power at a second temperature lower than the first temperature, and an efficiency at the first temperature is lower than an efficiency at the second temperature.

A power amplifier circuit includes: a transistor which is supplied at a base with a bias current, amplifies an input signal, and outputs a current; a transistor which is connected at a base to the base of the transistor and in which a current commensurate with the current is input to a collector; a transistor which outputs a bias control signal which controls supply of the bias current; and a control circuit which is connected to the collector of the transistor and a gate of the transistor and controls a bias control signal on the basis of a reference current based on a reference signal and the current.

A power amplifier circuit includes: a transistor which is supplied at a base with a bias current, amplifies an input signal, and outputs a current; a transistor which is connected at a base to the base of the transistor and in which a current commensurate with the current is input to a collector; a transistor which outputs a bias control signal which controls supply of the bias current; and a control circuit which is connected to the collector of the transistor and a gate of the transistor and controls a bias control signal on the basis of a reference current based on a reference signal and the current.

A differential tuned inductor and a multilayer tunable transformer for an integrated circuit device for microwave and RF applications are disclosed. The tunable inductor can be used in differential artificial delay lines to achieve delay tuning while preserving impedance matching. The tunable transformer can also be used for mixer drives to achieve wider operational performance.

A differential tuned inductor and a multilayer tunable transformer for an integrated circuit device for microwave and RF applications are disclosed. The tunable inductor can be used in differential artificial delay lines to achieve delay tuning while preserving impedance matching. The tunable transformer can also be used for mixer drives to achieve wider operational performance.

An RF transceiver front end includes a receiver limb including a length of transmission line, an impedance matching network, a downstream shunt switch and a downstream further receiver component and a transmitter limb. The impedance matching network is configured to transform the input impedance of the further receiver component to match the input impedance of the receiver limb when the shunt switch is open and the RF transceiver front end is operable in receiver mode. The impedance matching network is further configured to transform the input impedance of the shunt switch to present an open circuit as the input impedance of the receiver limb when the shunt switch is closed and the RF transceiver front end is operable in transmitter mode. The length of transmission line can be from zero to less than λ/4 at the operating frequency of the RF transceiver.

An RF transceiver front end includes a receiver limb including a length of transmission line, an impedance matching network, a downstream shunt switch and a downstream further receiver component and a transmitter limb. The impedance matching network is configured to transform the input impedance of the further receiver component to match the input impedance of the receiver limb when the shunt switch is open and the RF transceiver front end is operable in receiver mode. The impedance matching network is further configured to transform the input impedance of the shunt switch to present an open circuit as the input impedance of the receiver limb when the shunt switch is closed and the RF transceiver front end is operable in transmitter mode. The length of transmission line can be from zero to less than λ/4 at the operating frequency of the RF transceiver.

An acoustic wave device includes a silicon support substrate that includes first and second main surfaces opposing each other, a piezoelectric structure provided on the first main surface and including the piezoelectric layer, an IDT electrode provided on the piezoelectric layer, a support layer provided on the first main surface of the silicon support substrate and surrounding the piezoelectric layer, a cover layer provided on the support layer, a through-via electrode that extending through the silicon support substrate and the piezoelectric structure, and a first wiring electrode connected to the through-via electrode and electrically connected to the IDT electrode. The piezoelectric structure includes at least one layer having an insulating property, the at least one layer including the piezoelectric layer. The first wiring electrode is provided on the layer having an insulating property in the piezoelectric structure.

Methods and devices used in mobile receiver front end to support multiple paths and multiple frequency bands are described. The presented devices and methods provide benefits of scalability, frequency band agility, as well as size reduction by using one low noise amplifier per simultaneous outputs. Based on the disclosed teachings, variable gain amplification of multiband signals is also presented.

Methods and devices used in mobile receiver front end to support multiple paths and multiple frequency bands are described. The presented devices and methods provide benefits of scalability, frequency band agility, as well as size reduction by using one low noise amplifier per simultaneous outputs. Based on the disclosed teachings, variable gain amplification of multiband signals is also presented.