| 摘要 |
A first power source 11 for supplying a bias voltage to a gate electrode G of a field effect transistor 13 , which amplifies high-frequency signals, and a second power source 15 for supplying a bias voltage to a drain electrode D of the field effect transistor 13 are provided. The protective resistance 12 is connected between the gate electrode G of the field effect transistor 13 and the first power source 11 , and the bias voltage controller 14 is connected between the drain electrode D of the field effect transistor 13 and the second power source 11 . Further, a voltage detector 16 is connected between both ends of the protective resistance 12 to detect a voltage drop generated between both ends of the protective resistance 12 , when a rectified current flows to the gate electrode G from the drain electrode D of the field effect transistor 13.
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