| 摘要 |
A bias circuit 12 includes: a transistor Q 5 operable to supply, to an amplifier 11 , a bias current in accordance with a base current supplied thereto; a transistor Q 3 operable to pass a current in accordance with a reference voltage Vref; a transistor Q 2 operable to correct, in accordance with the current passed by the transistor Q 3 , the base current to be supplied to the transistor Q 5 , so as to compensate a temperature characteristic represented by the transistor Q 5 ; and a bias changing section (of a transistor Q 4 , and resistances R 5 , R 6 , and R 7 ), connected to a base of the transistor Q 5 , operable to change, in accordance with a control voltage VSW, an amount of the base current to be supplied to the transistor Q 5 . The amplifier 11 amplifies, by using the bias current supplied by the bias circuit 12 , a radio frequency signal having been inputted thereto.
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