US Patent 9209754 Amplifier with adjustable load

A device includes a Doherty amplifier having a carrier path and a peaking path. The Doherty amplifier includes a carrier amplifier configured to amplify a signal received from the carrier path and a peaking amplifier configured to amplify a signal received from the peaking path. The device includes a variable impedance coupled to an output of the Doherty amplifier, and a controller configured to set the variable impedance to a first impedance when an output power level of the Doherty amplifier is less than a threshold and to a second impedance when the output power level of the Doherty amplifier is above the threshold.