| 摘要 |
A bias circuit of a power amplifier is provided to operate stably by using an active element such as a transistor or a diode which drops a voltage applied by a mode voltage terminal when a high power output mode and a low power output mode are switched. A bias circuit of a power amplifier includes a power amplifier(50) and a bias applying unit(40). The power amplifier(50) amplifies an input signal by a predetermined amplifying ratio. The bias applying unit(40) includes an active element which drops a voltage applied by a mode voltage terminal. The active element is a diode and a transistor of which a collector is connected to a base. The bias applying unit(40) drops the voltage applied by the mode voltage terminal through the active element when being switched into a low power mode. The bias applying unit(40) prevents generation of a fault current when being switched into the low power mode. The stability of the bias circuit of the power amplifier having high efficiency is improved by switching the high power output mode and the low power output mode. |
