| 摘要 |
In order to supply a bias voltage to the base terminals of heterojunction bipolar transistors (HBTs) Q 1 to Q 3 connected in parallel to one another, resistors RB 1 to RB 3 and heterojunction bipolar transistors QB 1 to QB 3 whose base terminals are connected to the collector terminal thereof are provided. The amplifier transistors Q 1 to Q 3 have the same temperature characteristics as those of the bias-producing transistors QB 1 to QB 3 . With the bias circuit, it is possible to compensate for the temperature characteristics of the amplifier transistors Q 1 to Q 3 . Since the resistance values of the resistors RB 1 to RB 3 can be decreased, it is possible to suppress the decrease in the output power and to prevent the occurrence of the collapse phenomenon. Thus, it is possible to obtain a power amplifier capable of preventing the thermal runaway and compensating for the temperature characteristics without deteriorating the output characteristics.
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