The present invention relates to bias control of a power amplification
circuit of a mobile device for improving the efficiency and the linearity
properties of the power amplifier. In one embodiment, the power amplifier
improves these properties by receiving a voltage control signal to bias a
supplemental amplifier so that the power amplifier operates in a Doherty
mode in a low output power range and in a non-Doherty mode in a high
output power range. In the non-Doherty mode, the supplemental amplifier
is biased as a class AB amplifier via the received voltage control signal
to satisfy the non-linear operational requirements of the power amplifier
in the high output power range. The power amplifier generates the voltage
control signal based upon power levels of signals received from a remote
base station.