| 摘要 |
PROBLEM TO BE SOLVED: To provide a high frequency power amplifier that continuously controls an output power by changing a drain voltage of a switching-driven FET and has an enhanced efficiency than that of a conventional power amplifier adopting a similar system. SOLUTION: The high frequency power amplifier is provided with amplifiers PA(1) 11 , PA(2) 12 adopting the switching-driver EFTs connected in parallel, a fixed drain voltage +B is applied to the amplifier PA(2), and a variable drain voltage is applied to the amplifier PA(1) through a means 11 (DC-DC converter 4) that converts a bias +B depending on a control variable of a CONT(1). A CONT(2) controls ON/OFF of the operation of the PA(2) and varies a circuit constant of a matching circuit 4 at the same time. The PA(2) is active at a high output region and deactivated at a low output region to minimize the deteriorating in the efficiency by the DC-DC converter 4, and the matching is taken again in the ON/OFF state of the PA(2) to enhance the efficiency and to attain continuous control of the output.
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