| 摘要 |
PURPOSE:To improve input/output characteristics and to obtain a sufficient power gain in a high frequency range by applying a DC bias between a base and an emitter in a power amplifier using a hetero junction bipolar transistor. CONSTITUTION:A DC bias smaller than the ON voltage of a hetero junction bipolar transistor (HBT) 11 is applied between the base and the emitter of the input side of the HBT11 by the HBT11 having narrower band gap of a base region than that of an emitter region as an element having an amplifying operation. That is, a DC power source 18 is connected between an input matching circuit 15a and the HBT11. A reactance L19 between the power source 18 and the emitter E of the HBT is a reactance for cutting an AC. When the amplifier constructed in this manner is operated, a high frequency operation is performed, and a sufficient power gain can be obtained.
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