US Patent 10110168 Multi-mode stacked amplifier

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.