Patent ID: 7990220

Claim:
An RF power amplifier comprising: a first transistor and a second transistor each as an active device of a push-pull power amplification circuit; and a transformer as an output matching circuit of the push-pull power amplification circuit, wherein a non-inverted input signal and an inverted input signal can be supplied respectively to an input terminal of the first transistor and an input terminal of the second transistor, wherein the transformer has a primary coil and a secondary coil which are magnetically counted to each other, wherein one end and the other end of the primary coil of the transformer are coupled respectively to an output terminal of the first transistor and an output terminal of the second transistor, wherein an output signal can be generated from between one end and the other end of the secondary coil of the transformer, and wherein the primary coil of the transformer includes at least a first coil and a second coil which are coupled in parallel between the output terminal of the first transistor and the output terminal of the second transistor, and each being magnetically coupled to the secondary coil, wherein at least one of the first coil and the second coil can be supplied with a power supply voltage between the output terminal of the first transistor and the output terminal of the second transistor, wherein the primary coil and the secondary coil of the transformer are formed of respective metal thin-film wires having annular shapes, and each being formed in a flat shape over a surface of a substrate, and wherein the metal thin-film wire forming the primary coil of the transformer is formed to have a width larger than a width of the metal thin-film wire forming the secondary coil of the transformer.