| 摘要 |
An amplifier system includes a power amplifier which generates undesired distortion in its main output signal, and a distortion detecting circuit for detecting distortion spectrums included in the main output signal so as to output a distortion level indicating signal by attaining a difference of a main input signal having no distortion and a monitor signal representing the main output signal while the main input signal and the monitor signal are kept in phase and equal in level. The amplifier system also includes compensation circuit, provided at the input of the amplifier, for adding a compensation signal, to the main input signal which is to be equivalent generated equivalently to the distortion in the main output signal. The amplifier system further includes and a control circuit for precisely adjusting phase and level of the compensation signal so as to keep the distortion level indicating signals minimum. Phase/level adjustment in the distortion detecting circuit by minimizing the signal component remaining in the difference signal allows for better detection of the distortion component. Thus, less expensive filters can by employed in the distortion detecting circuit. The above-described automatic distortion compensation may be disabled when the main input signal is lower than a threshold level, where the automatic compensation operation becomes unnecessary and unstable.
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