本发明之态样系关于一种包括一堆栈式放大器及一偏压电路之放大电路。该堆栈式放大器包括彼此串联之至少一第一晶体管与一第二晶体管。该堆栈式放大器可在至少一第一模式及一第二模式下操作。该偏压电路经组态以在该第一模式下使该第二晶体管偏压至一线性操作区，且经组态以在该第二模式下使该第二晶体管偏压为一开关。在某些实施例中，该放大电路可系一功率放大器级，该功率放大器级经组态以接收在该第一模式下具有与在该第二模式下不同之一电压位准的一供应电压。

Aspects of this disclosure relate to an amplification circuit that includes a stacked amplifier and a bias circuit. The stacked amplifier includes at least a first transistor and a second transistor in series with each other. The stacked amplifier is operable in at least a first mode and a second mode. The bias circuit is configured to bias the second transistor to a linear region of operation in the first mode and to bias the second transistor as a switch in the second mode. In certain embodiments, the amplification circuit can be a power amplifier stage configured to receive a supply voltage that has a different voltage level in the first mode than in the second mode.