| 摘要 |
A power amplifier of amplifying signals of two frequency bands is reduced in size and improved in efficiency at low output. The power amplifier includes an input terminal, a branch circuit and so on having one input and a plurality of outputs, the input being connected to the input terminal, amplifying means which are connected to some outputs of the branch circuit and so on and are operated at different signal frequencies from each other, a transmission line connected to one of the other outputs of the branch circuit, a synthesizing circuit connected to the outputs of the amplifying means and the output from the transmission line, a switch provided between the transmission line and a synthesis output unit, and a control circuit of controlling conduction of the branch circuit and so on, conduction and an amplifying operation of the amplifying means, and conduction of the switch.
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