Patent ID: 7567128
Filing Date: 2009-07-28
Classification: H03F

Abstract:
1. A power amplifier comprising: a power amplification element; and an output matching circuit connected to an output end of said power amplification element; wherein said output matching circuit includes a plurality of trap circuits establishing short-circuit at frequencies higher than a desired transmission frequency band and at frequencies different from each other, out of at least two trap circuits among said plurality of trap circuits, the trap circuit higher in frequency at which short-circuit is established is arranged closer to the output end of said power amplification element than the trap circuit lower in frequency at which short-circuit is established, the trap circuit arranged closer to the output end of said power amplification element is set such that a frequency at which short-circuit is established is more than twice as high as a central frequency of said desired transmission frequency band and impedance of said output matching circuit on a side of the output end of said power amplification element is substantially short-circuited with respect to at least one frequency in a frequency band twice as high as said desired transmission frequency band, and the trap circuit lowest in frequency at which short-circuit is established among said trap circuits is set such that a frequency at which short-circuit is established is at least 1.4 times as high as a frequency highest in said desired transmission frequency band and less than twice as high as the central frequency of said desired transmission frequency band.