Sony United Kingdom Limited

Simon Denny

Anthony Eaton

To effect power control of a power amplifierhaving three amplifier stagesandused to amplify input signals modulated in accordance with a variable envelope modulation scheme, there is used a power amplifierhaving a gain which reduces as the supply voltage to the power amplifierreduces, and the output power Pof the power amplifieris controlled by regulation of the supply voltage V. Taking advantage of the reduction in gain of the power amplifier, it is ensured that, in respect of each respective amplifier stageandand at each respective value of the supply voltage in the voltage control range, the output power Pof the respective amplifier stageandis less than the saturation output power Pof the respective amplifier stageand. As a result, distortion of the signal is reduced. The power control technique improves efficiency over known techniques of backing off the output power and using a variable gain amplifier stage to control the output power.

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Basingstoke, United Kingdom

Simon Denny