Patent ID: 7847630

Claim:
A Doherty amplifier for combining outputs of a plurality of amplifying circuits to generate an amplifier output, comprising: a first amplifying circuit for operating a first amplifying device in class-AB, wherein the first amplifying circuit is one among the plurality of the amplifying circuits, and the first amplifying circuit includes an output matching circuit at an output side thereof; a second amplifying circuit for operating a second amplifying device in class-B or class-C, wherein the second amplifying circuit is one among the plurality of the amplifying circuits; and a summing node at which an output of the first amplifying circuit is combined with an output of the second amplifying circuit via a first impedance transformer containing a transmission line and the impedance transformer is other than a multiple of λ/4, wherein when a load impedance value of the output matching circuit is substantially equal to an impedance value of the first impedance transformer, an output power of the output matching circuit is a maximum power of the first amplifying circuit, and wherein an electrical length of the transmission line is adjusted so that an amplifying efficiency of the first amplifying circuit is maximum within an input level region where the first amplifying circuit operates alone and wherein between a second output matching circuit of the second amplifying circuit and the summing node is a straight line.