Patent ID: 7733185

Claim:
A distributed amplifier for amplifying a signal applied to an input terminal and including components in a predetermined frequency range to deliver the amplified signal from an output terminal, said distributed amplifier comprising: a plurality of transistors which operate as amplification elements; an input side coupling circuit including a plurality of distributed constant lines connected in series, one terminal of which is the input terminal, and another terminal of which is a bias input terminal, wherein each of the connections of said distributed constant lines with each other is connected to an input of each of said plurality of transistors; an output side coupling circuit including a plurality of distributed constant lines connected in series, one terminal of which is the output terminal, and another terminal of which is a bias input terminal, wherein each of the connections of said distributed constant lines with each other is connected to an output of each of said plurality of transistors; and a termination circuit contained in at least one of said input side coupling circuit and said output side coupling circuit, including an inductor connected to a voltage source, a first resistor connected between the bias input terminal and the inductor, and a second resistor connected between the bias input terminal and a ground potential, wherein said first resistor has a resistance value equal to or smaller than a resistance value of said second resistor, and the resistance value of said first resistor, the resistance value of said second resistor, and an inductance value of said inductor are selected, such that an impedance of an equivalent circuit which has a series connected circuit of said first resistor and said inductor and has said second resistor connected in parallel with said series connected circuit, has an impedance value within a predetermined range in the predetermined frequency range.