| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-frequency amplifier by which a fluctuation in the idle current of an RF (Radio Frequency) transistor is suppressed and the efficiency of the amplifier is enhanced. SOLUTION:Åbase bias in the high power output mode of an RF transistor 1 and the base bias in a low power output mode are provided by separate power sources, respectively. The base bias is outputted from a bias circuit 3 when the amplifier 30 is in the high power output mode. At this time, the RF transistor 1 carries out constant voltage operation by a set bias output from the bias circuit 3. The base bias is supplied through a resistor R3 (12) from a reference voltage Vref terminal 5 when the amplifier 30 is in the low power output mode. Thus, a fluctuation in the base bias set voltage is reduced. The non-operation of the bias circuit 3 makes consumption current of the bias circuit section 3 not flow in the low power output mode, enhancing the efficiency of the amplifier 30. COPYRIGHT: (C)2004,JPO
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