Power amplifier systems with switchable transistor array and switchable biasing circuit

A mobile device comprising:

• a transceiver configured to generate a radio frequency input signal;
• and
• a front-end system including a power amplifier system operable in selected power mode chosen from a plurality of power modes, the power amplifier system including a power amplifier having a transistor array configured to amplify the radio frequency input signal to generate a radio frequency output signal, and a power amplifier biasing circuit configured to control both a number of active transistors of the transistor array and a bias of the power amplifier based on the selected power mode, the transistor array including a first power amplifier transistor and a second power amplifier transistor electrically connected in parallel between an input that receives the radio frequency input signal and an output that provides the radio frequency output signal, the power amplifier biasing circuit configured to activate both the first power amplifier transistor and the second power amplifier transistor in a first power mode of the two or more power modes, to activate the second power amplifier transistor and deactivate the first power amplifier transistor in a second power mode of the two or more power modes, and to bias the first power amplifier transistor with a first bias signal and the second power amplifier transistor with a second bias signal, the first power amplifier transistor being a first field effect transistor having a gate configured to receive the first bias signal, and the second power amplifier transistor being a second field effect transistor having a gate configured to receive the second bias signal.