Patent ID: 6903608

Claim:
A power amplifier circuit comprising: an input port for receiving a RF input signal; an output port for providing therefrom a RF output signal, the RF output signal being an amplified version of the RF input signal; a supply voltage input port for receiving a supply voltage; a controllable current source having an input port for receiving a control signal and an output port for providing of a variable bias current therefrom, the variable bias current based upon the control signal; a first amplification stage having a first variable gain and for receiving the RF input signal and for providing a first amplified RF signal, the first amplification stage coupled to the controllable current source for receiving the variable bias current therefrom and for having the first variable gain thereof varied in proportion to the variable bias current; a second amplification stage having a second gain and coupled to the first amplification stage for receiving the first amplified RF signal and coupled to the output port for providing the output signal thereto; and, a control circuit for generating the control signal for provision to the controllable current source, the control signal for being generated in dependence upon the supply voltage, where for the supply voltage having a first potential the variable bias current provided to the first amplification stage is smaller than for the supply voltage having a second potential that is lower than the first potential.