Patent ID: 6674323
Filing Date: 2004-01-06
Classification: H03F

Abstract:
A high frequency power amplifier comprising:a first amplifying circuit having a first output stage including a first transistor; a second amplifying circuit having a second output stage including a second transistor having a size equal to or smaller than Â¼ of a size of the first transistor; a switching circuit connected between a signal line at the first amplifying circuit frontward from the first output stage and a ground terminal; an input terminal constituted by an input line of the first amplifying circuit and an input line of the second amplifying circuit to each other; and an output terminal constituted by connecting an output line of the first amplifying circuit and an output line of the second amplifying circuit to each other, wherein the first amplifying circuit outputs a high frequency signal at a first output level to the output terminal when the switching circuit is brought into an off state and the second amplifying circuit is brought into a nonoperational state, and wherein the second amplifying circuit outputs a high frequency signal at a second output level lower than the first output level when the switching circuit is brought into an on state and the first amplifying circuit is brought into the nonoperational state.