| 摘要 |
To provide a variable gain power amplifier with wide dynamic range of transmission power, wherein power efficiency is high, distortion in the linearity is low. In an amplifier with a plurality of transistors connected with cascade, the source of transistor (103) is grounded, the gate of transistor (108) of an output stage is grounded. Further, source bias terminal (109) and drain bias terminal (110) is provided for applying prescribed voltages to the source and drain of transistor (108) of the output stage, respectively. The electric power inputted into transistor (108) of the output stage is passed through without being amplified by applying the prescribed voltages to source bias terminal (109) and drain bias terminal (110), respectively, when the electric power outputted from the output stage is made smaller than a prescribed threshold.
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