A two- (or multi) stage power
amplifier receives a variable RF input
signal, and outputs an optimized. RF output
signal from, for example, a mobile
handset. The output
power level from the
handset is predetermined, as known in the art, by the received
control signal from a
base station. The first power
amplifier stage amplifies the variable RF input
signal and outputs an RF signal, Vin, to a
power detector circuit and an RF signal to the second or next
amplifier stage. The power detect circuit amplifies the Vin signal and rectifies that signal with a linearly biased
diode and provides a detect signal to a
DC to DC converter. The converter responds by providing an optimum
voltage bias, which is linearly related to the
DC voltage detect signal from the
power detector, to the output stage, and, if desired, to the first and / or other stages of the power amplifier that optimizes the output
power level while meeting the required
linearity specification. The battery
current consumption is optimized through this automatic, dynamically control of the supply
voltage for the power amplifier at each output
power level through the
DC to DC converter.