Abstract: A bias circuit 12 includes: a transistor Q5 operable to supply, to an amplifier 11, a bias current in accordance with a base current supplied thereto; a transistor Q3 operable to pass a current in accordance with a reference voltage Vref; a transistor Q2 operable to correct, in accordance with the current passed by the transistor Q3, the base current to be supplied to the transistor Q5, so as to compensate a temperature characteristic represented by the transistor Q5; and a bias changing section (of a transistor Q4, and resistances R5, R6, and R7), connected to a base of the transistor Q5, operable to change, in accordance with a control voltage VSW, an amount of the base current to be supplied to the transistor Q5. The amplifier 11 amplifies, by using the bias current supplied by the bias circuit 12, a radio frequency signal having been inputted thereto.

Abstract: A bias circuit 12 includes: a transistor Q5 operable to supply, to an amplifier 11, a bias current in accordance with a base current supplied thereto; a transistor Q3 operable to pass a current in accordance with a reference voltage Vref; a transistor Q2 operable to correct, in accordance with the current passed by the transistor Q3, the base current to be supplied to the transistor Q5, so as to compensate a temperature characteristic represented by the transistor Q5; and a bias changing section (of a transistor Q4, and resistances R5, R6, and R7), connected to a base of the transistor Q5, operable to change, in accordance with a control voltage VSW, an amount of the base current to be supplied to the transistor Q5. The amplifier 11 amplifies, by using the bias current supplied by the bias circuit 12, a radio frequency signal having been inputted thereto.

Abstract: A bias circuit 12 includes: a transistor Q5 operable to supply, to an amplifier 11, a bias current in accordance with a base current supplied thereto; a transistor Q3 operable to pass a current in accordance with a reference voltage Vref; a transistor Q2 operable to correct, in accordance with the current passed by the transistor Q3, the base current to be supplied to the transistor Q5, so as to compensate a temperature characteristic represented by the transistor Q5; and a bias changing section (of a transistor Q4, and resistances R5, R6, and R7), connected to a base of the transistor Q5, operable to change, in accordance with a control voltage VSW, an amount of the base current to be supplied to the transistor Q5. The amplifier 11 amplifies, by using the bias current supplied by the bias circuit 12, a radio frequency signal having been inputted thereto.

Abstract: A bias circuit 12 includes: a transistor Q5 operable to supply, to an amplifier 11, a bias current in accordance with a base current supplied thereto; a transistor Q3 operable to pass a current in accordance with a reference voltage Vref; a transistor Q2 operable to correct, in accordance with the current passed by the transistor Q3, the base current to be supplied to the transistor Q5, so as to compensate a temperature characteristic represented by the transistor Q5; and a bias changing section (of a transistor Q4, and resistances R5, R6, and R7), connected to a base of the transistor Q5, operable to change, in accordance with a control voltage VSW, an amount of the base current to be supplied to the transistor Q5. The amplifier 11 amplifies, by using the bias current supplied by the bias circuit 12, a radio frequency signal having been inputted thereto.