a linearized power amplifier is provided which comprises a non - linear radio frequency power amplifier , a linearization circuit such as a cartesian feedback circuit , an rf feedback circuit ; an if feedback circuit ; or a feedforward circuit , and a dynamic bias modulation circuit for modulating an operating voltage of the amplifier . the dynamic bias modulation means includes an envelope determining circuit , signal processing circuits in which predetermined data or a simplified transfer function determined from measured characteristics of the amplifier is stored and used to produce power bias and / or base or gate bias signals , and driver circuits for modulating the power supply voltage and / or base or gate bias voltage of the rf amplifier in response to the bias signals . the dynamic bias modulation may be used with a bjt - based , and fet - based or any other type of rf power amplifier . with the right combination of power supply and base or gate bias modulation the efficiency of the rf amplifier can be maximised for a given output power , and the combination of linearization means and high level power supply and / or base or gate bias modulation gives the benefits of improved spectral control and intermodulation distortion reduction coupled with high efficiency .