Patent ID: 7427895
Filing Date: 2008-09-23
Classification: H03F

Abstract:
1. An amplifier apparatus comprising: an input terminal to receive an input signal to be amplified; a divider to divide the input signal into a first divided signal and a second divided signal; a carrier amplifier to amplify the first divided signal by operating as a class AB with a first conduction angle and produce a first amplified signal; a variable attenuator to attenuate the second divided signal in accordance with a variable attenuation amount; a peak amplifier to amplify the second divided signal attenuated by the variable attenuator to produce a second amplified signal; a first control unit configured to control a bias applied to the peak amplifier to (a) make the peak amplifier operate as a class C when a level of the input signal is lower than a first threshold value, to (b) make the peak amplifier operate as the class AB with a second conduction angle substantially equal to the first conduction angle, when the level of the input signal is higher than a second threshold value higher than the first threshold value, and to (c) make the peak amplifier operate as the class AB with a third conduction angle smaller than the first conduction angle, when the level of the input signal is not less than the first threshold value and not more than the second threshold value; a second control unit configured to control the variable attenuator for increasing the attenuation amount in accordance with an increase in the level of the input signal; a combiner to combine the first amplified signal and the second amplified signal and produce an amplified output signal; and a signal output terminal to output the amplified output signal.