Fujitsu Corporation

Hisao Shigematsu

Hitoshi Tanaka

Kenji Imanishi

Norikazu Nakamura

Junji Kotani

A compound semiconductor device includes a substrate, a compound semiconductor layer formed over the substrate, a channel layer formed over the compound semiconductor layer, an electron supply layer formed over the channel layer, and a source electrode, a drain electrode, and a gate electrode that are formed apart from each other over the electron supply layer. A quantum well structure is formed by the compound semiconductor layer, the channel layer, and the electron supply layer.

Compound semiconductor device with quantum well structure, power supply device, and high-frequency amplifier

An amplifier according to the present invention includes an amplifying transistor, and an impedance converter circuit coupled to an output unit of the amplifying transistor and including a plurality of impedance converting transistors different in input impedance, which are series-connected.

Amplifier

In order to allow to make compact a distributed amplifier by dispensing with any choke coil and reduce its cost, the distributed amplifier is configured such that it comprises an input side transmission line, an output side transmission line, and plural amplifier circuits connected to the input side transmission line and the output side transmission line, wherein push-pull amplifier circuits are employed as the amplifier circuits.

Distributed amplifier

A resistor (-) and a resistor (-) are connected in parallel with each other between a source of an input transistor (-) and the ground. A switch (-) is provided between the resistor (-) and the source. A variable resistor circuit may be constituted by the resistor (-), the resistor (-) and the switch (-). Further, a capacitor (-) and a variable capacitor (-) are connected in series with each other between the source and the ground. A control terminal (-) to which a voltage is applied when capacitance of the variable capacitor (-) is controlled is provided between the capacitor (-) and the variable capacitor (-). A variable capacitor circuit may be constituted by the capacitor (-) and the variable capacitor (-). An input capacitance change circuit may be constituted by the variable resistor circuit and the variable capacitor circuit.

Analog circuit

An oscillator circuit includes first and second transistors forming a differential pair, an output combiner connected to first terminal sides of the first and second transistors, and a current source connected to second terminal sides of the first and second transistors.

Oscillator circuit

A multi-stage amplifier includes first and second amplifier stages, and first and second capacitors. The first amplifier stage includes a input line having a first input end and a second input end; an input terminal block connected to the second input end; an amplifier circuit amplifying a first signal input to the first input end; an output line having a first output end where the first signal amplified is output, and a second output end; and an output terminal block connected to the second output end. The second amplifier stage includes components similar to that of the first amplifier stage. The first capacitor is connected between the first output end of the first amplifier stage and the first input end of the second amplifier stage. The second capacitor is connected to any one of the input and output terminal blocks of the first and second amplifier stages.

Multi-stage amplifier

In a cascode distributed amplifier of the present invention, a plurality of unit circuits are connected in parallel, and each unit circuit includes a pair of first and second transistors connected in series between an input transmission wire and an output transmission wire. The first transistor has a gate connected to the input transmission wire, a source grounded and a drain connected to the second transistor. The second transistor has a gate grounded, a source connected to the drain of the first transistor and a drain connected to the output transmission wire. Each unit circuit includes a damping resistor having a first end connected to the gate of the second transistor and a second end, and a capacitor having a first end connected to the second end of the damping resistor and a second end grounded.

Cascode distributed amplifier

A plurality of amplifying circuits to are connected between input and output transmission circuits and in a forward direction, a bias-T is connected to an output terminal OUT of the transmission circuit and a DC bias voltage VDD is applied to the outputs of the amplifying circuits to through the inductor of the circuit and the transmission circuit The opposite end to the output terminal OUT is grounded through a series connection of a terminating resistor R and a DC voltage source having an output voltage VDD Since VDD &equals;VDD the DC voltage across the terminating resistor R is zero. The inductor may be connected in parallel to the terminating resistor R with omitting the bias voltage VDD

Distributed amplifier with terminating circuit capable of improving gain flatness at low frequencies

The semiconductor device comprises a collector layer ; a base layer of a carbon-doped Ga In As Sb layer having one surface connected to the collector layer ; an emitter layer connected the other surface of the base layer ; a base contact layer of a carbon-doped GaAsSb layer electrically connected to the base layer ; and a base electrode 32 formed on the base contact layer . The semiconductor device of such structure can have a much reduced base resistance R , whereby InP/GaInAsSb-based HBTs including InP/InGaAs-based HBTs can have higher maximum oscillation frequency f . Because of the carbon-doped semiconductor layer the semiconductor device can have higher reliability.

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Kawasaki, Japan

Hisao Shigematsu