| 摘要 |
PROBLEM TO BE SOLVED: To provide a power amplifier including appropriate power efficiency and linearity corresponding to different output power modes.SOLUTION: An RF output power amplifier 8 of a cellular telephone includes first and second Class-AB amplifier circuits 109, 110. If the cellular telephone is to operate in a high power operating mode, then the first amplifier 109 drives a PA output terminal 117. The power transistor(s) 121 in the first amplifier 109 is/are biased at a first DC current and a first DC voltage so as to optimize efficiency and linearity at high output powers. If the cellular telephone is to operate in a low power operating mode, then the second amplifier 110 drives the output terminal 117. The power transistor(s) 124, 125 in the second amplifier 110 is/are biased at a second DC current and a second DC voltage so as to optimize efficiency and linearity at low output powers. |
