Systems and methods for a tunable impedance are provided. A tunable impedance includes a transistor assembly having two terminals and a control input. The transistor assembly includes one or more transistors electrically connected between the two terminals to provide a first impedance between the two terminals, based upon a control signal. One or more replica transistors react to the control signal in a similar fashion as the transistor assembly, to provide a replica impedance based upon the control signal. A control circuit is configured to generate the control signal based upon a voltage across the replica transistor(s) and/or a current through the replica transistor(s).

A power amplifier circuit includes an amplifier that amplifies an input signal RFin, a matching circuit that provides impedance matching between an output port of the amplifier and an output terminal, an input of the matching circuit being connected to the output port of the amplifier, an output of the matching circuit being connected to the output terminal, and a resonant circuit provided between ground and a signal path that connects the output port of the amplifier and the input of the matching circuit, the resonant circuit resonating at a resonant frequency greater than or equal to the frequency of a fourth harmonic wave of an amplified signal obtained by amplifying the input signal.

Embodiments of the present disclosure include a harmonic power amplifying circuit with high efficiency and high bandwidth and a radio-frequency power amplifier. The circuit comprises an input matching network (11), a transistor (M), and an output matching network (12); a gate of the transistor (M) connected to an output end of the input matching network (11), a drain thereof connected to an input end of the output matching network (12), and a source thereof being grounded; wherein the output matching network (12) enables a lower sideband of the harmonic power amplifying circuit to work in a continuous inverse F amplification mode and an upper sideband of the harmonic power amplifying circuit to work in a continuous F amplification mode; wherein the output matching network (12) and a parasitic network of the transistor (M) form a low pass filter. By transitioning from the continuous inverse F power amplifier working mode to the continuous F power amplifier working mode, the efficiency of a continuous harmonic control power amplifier is effectively improved to be higher than 60%, a relative bandwidth is improved to be higher than 80%, and the harmonic impedance is simple to match and easy to realize.

Apparatus including a first transmission line for transmitting radio frequency, RF, signals and at least one RF device including at least one active semiconductor device for processing RF signals, wherein said at least one RF device is coupled to said first transmission line, and wherein said first transmission line includes an electro-chromic, EC, material a permittivity of which can be controlled by applying a first control voltage to said first transmission line.

An amplifier is formed in a wiring layer. A semiconductor device includes a second layer over a first layer with a metal oxide therebetween. The first layer includes a first transistor including a first semiconductor layer containing silicon. The second layer includes an impedance matching circuit, and the impedance matching circuit includes a second transistor including a second semiconductor layer containing gallium. The first transistor forms first coupling capacitance between the first transistor and the metal oxide, and the impedance matching circuit forms second coupling capacitance between the impedance matching circuit and the metal oxide. The impedance matching circuit is electrically connected to the metal oxide through the second coupling capacitance. The metal oxide inhibits the influence of first radiation noise emitted from the impedance matching circuit on the operation of the first transistor.

An amplifier (T1) amplifies an input signal. A harmonic matching circuit (3) is connected to an output end of the amplifier (T1) via a first wire (W1). The harmonic matching circuit (3) includes a first inductor (L1) connected to the first wire (W1), a first capacitor (C1) connected in series to the first inductor (L1), a second inductor (L2) connected in parallel with the first inductor (L1), and a second capacitor (C2) connected in series to the second inductor (L2). The first inductor (L1) and the second inductor (L2) form a subtractive-polarity coupler which presents mutual inductance having subtractive polarity.

A high frequency circuit includes a transistor amplifying a high frequency signal, and having an input electrode and an output electrode, a line that is connected to any one of the input electrode and the output electrode, and transmits a high frequency signal or an amplified high frequency signal, a bias terminal to which a bias voltage is supplied, a bias circuit that has a first end connected to a first node and a second end connected to the bias terminal, and suppresses a high frequency signal having a frequency within an operating frequency band of the transistor from passing from the first node to the bias terminal, and a resonance circuit that is connected between a reference potential and a second node provided between the bias terminal and the bias circuit, and minimizes an impedance between the second node and the reference potential at a resonance frequency.

A radio frequency power amplifier and a device are disclosed. A first microstrip line and a second microstrip line are coupled, one end of the second microstrip line is an open stub and another end of the second microstrip line is grounded; and the first microstrip line having a first width is connected to a first transmission line having a second width which is wider than the first width. Therefore, some harmonic bands suppression can be implemented independently. Furthermore, the harmonic termination is independent and may not impact one or more fundamental components during matching a network. In addition, it may not take up more space and is sufficiently compact. Furthermore, sufficient wide harmonic response bandwidth can be provided.

A digital-to-analog converter (DAC) circuit includes a pair of output stages, each including a DAC configured to convert a digital audio signal into an analog audio signal. A low-pass filter circuit includes an operational amplifier in signal communication with the DAC. The operation amplifier generates a filtered analog signal based on the analog audio signal. An amplifier network generates an amplified audio signal based on the filtered analog signal. The operational amplifier includes a feedback circuit path including a first node connected to the output of the amplifier network and a second node connected to the input of the operational amplifier. The amplifier network is electrically nested in the feedback circuit path.

Devices and methods for implementing an RF integrated circuit device operatively configured to provide the function of RF power splitter with programmable output phase shift are described. Configurable and adjustable phase shift units for use in such IC device are also described.