Image Number 2 for United States Patent #7560989.
The invention includes a power amplifier with an amplifier core including parallel amplifier cells, a replica cell made of one amplifier cell similar to those of the amplifier core, a power controller to select a combination of amplifier cells to activate, a regulator to fix the top voltage of the replica cell to a reference voltage, a voltage generator to provide the voltage reference to the regulator, a current generator to provide a reference current through the replica cell, and a drive unit controlled by the regulator output to drive the combination of amplifier cells, so that each selected combination of activated cells defines a predetermined attenuation level of power amplifier output signal so that it is attenuated in a stepwise manner.
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