Example embodiments relate to push-pull class E amplifiers. One example push-pull class E amplifier includes an input configured for receiving a signal to be amplified. The push-pull class E amplifier also includes an output configured for outputting the signal after amplification. Additionally, the push-pull class E amplifier includes a printed circuit board having a first dielectric layer and a second dielectric layer. Further, the push-pull class E amplifier includes a first amplifying unit and a second amplifying unit. Yet further, the push-pull class E amplifier includes a balun, a capacitive unit, a first line segment, a second line segment, a third line segment, and a fourth line segment. The first line segment and the second line segment are arranged on the first dielectric layer. A combined length of the third line segment and the fourth line segment corresponds to a quarter wavelength of an operational frequency of the amplifier.

A microwave amplifier having a load network which provides more efficient amplification of a low power microwave frequency signal. The amplifier comprises a transistor and a load network coupled to the transistor output to shape a waveform of an amplified microwave signal at the transistor current source plane. The load network comprises: a fundamental matching network to provide impedance matching at a fundamental frequency; a half-wave transmission line for a second harmonic frequency disposed between the transistor output and the fundamental matching network; a quarter-wave stub and a five-quarter-wave stub for a third harmonic frequency arranged on the half-wave transmission line to provide an open circuit condition at the third harmonic; and a quarter-wave stub for the second harmonic frequency and a quarter-wave stub for the fundamental frequency, arranged on the half-wave transmission line to provide a short circuit condition at the second harmonic frequency.

A stub whose end is connected to an end of a transmission line, and a coupled line disposed in parallel with each of the transmission line and the stub, and electromagnetically coupled to each of the transmission line and the stub are included, and the stub and the coupled line operate as a first resonator for resonating with an odd order harmonic included in the amplified signal, and the transmission line, the stub, and the coupled line operate as a second resonator for resonating with an even order harmonic included in the amplified signal.

To provide a mixer and a semiconductor device which each have a small circuit area and each of which operation capability is inhibited from being decreased due to heat. The mixer includes a differential portion, a current source, a first load, an input terminal, and a first output terminal; the differential portion includes a first and a second transistor; and each of the first and the second transistors includes a metal oxide in a channel formation region. A first terminal of each of the first and the second transistors is electrically connected to the input terminal and a current source and a second terminal of the first transistor is electrically connected to a first terminal of the first load and the first output terminal. The first load has a function of supplying a current between the first terminal and a second terminal of the first load by application of voltage to the second terminal of the first load, and the current source has a function of supplying a constant current to the current source from the first terminal of each of the first and the second transistors. The current source includes a transistor including silicon in a channel formation region, and the differential portion is positioned above the current source.

In a semiconductor device including gate fingers each having a linear shape extending from a feed line, and arranged in areas between drain electrodes and source electrodes, open stubs are connected directly to the feed line.

A radio frequency circuit has an amplifier that amplifies an input radio frequency signal, a power supply path that is disposed between an output node of the amplifier and a power supply node to which a DC bias voltage is supplied, and includes a first inductor and a second inductor connected in series, a first resonator that comprises a third inductor and a first capacitor connected in series to the third inductor, and resonates at a series resonance frequency, a second resonator that resonates at a series resonance frequency corresponding to an inductance of the first inductor, a capacitance of the second capacitor, and a resistance value of the first resistor, and a third resonator that comprises a third capacitor connected in parallel with the second inductor, and resonates at a parallel resonance frequency corresponding to a capacitance of the third capacitor and an inductance of the second inductor.

A variable gain circuit includes: input/output terminals P1 and P2 configured to input/output a high frequency signal; a transistor having a signal terminal “a” connected to the input/output terminal P1, a signal terminal “b” connected to the input/output terminal P2, and a control terminal; bias terminals B1, B2 and B3, and a reference voltage terminal respectively set to a first variable voltage, a second variable voltage, a third variable voltage, and a fixed voltage that are independent of one another; an impedance element connected between the bias terminal B1 and the signal terminal a; an impedance element connected between the bias terminal B2 and the signal terminal b; an impedance element connected between the bias terminal B3 and the control terminal; and a first switch configured to switch between connecting and not connecting the reference voltage terminal and the control terminal.

Apparatus and methods for an inverted Doherty amplifier operating at gigahertz frequencies are described. RF fractional bandwidth and signal bandwidth may be increased over a conventional Doherty amplifier configuration when impedance-matching components and an impedance inverter in an output network of the inverted Doherty amplifier are designed based on characteristics of the main and peaking amplifier and asymmetry factor of the amplifier.

A variable gain amplifier (VGA) is provided. The VGA includes at least one amplifier circuit, at least one current-steering circuit and at least one bias voltage circuit. Each current-steering circuit is coupled to its corresponding amplifier circuit. Each bias voltage circuit is coupled to its corresponding current-steering circuit to provide a positive bias voltage to each current-steering circuit.

Provided is a high-frequency amplifier capable of making a circuit substrate small and reducing a cost. A high-frequency amplifier is provided with a first substrate including a matching unit, and a second substrate including a transistor and a first impedance converter connected to each other, in which the matching unit of the first substrate and the first impedance converter are connected to each other via a first connection. Furthermore, the high-frequency amplifier is further provided with a third substrate including a matching unit, in which the second substrate may further include a second impedance converter connected to the transistor, and the second impedance converter and the matching unit of the third substrate may be connected to each other via a second connection.