Patent attributes
In order to supply a bias voltage to the base terminals of heterojunction bipolar transistors (HBTs) Q1 to Q3 connected in parallel to one another, resistors RB1 to RB3 and heterojunction bipolar transistors QB1 to QB3 whose base terminals are connected to the collector terminal thereof are provided. The amplifier transistors Q1 to Q3 have the same temperature characteristics as those of the bias-producing transistors QB1 to QB3. With the bias circuit, it is possible to compensate for the temperature characteristics of the amplifier transistors Q1 to Q3. Since the resistance values of the resistors RB1 to RB3 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.
