A power amplifying circuit detects the crest factor of an electric signal, especially an audio signal, requiring amplification. In case this crest factor is great, the level of supply voltage for power amplifying elements of the power amplifying circuit is raised, and conversely in case the crest factor...http://www.google.com/patents/US4348644?utm_source=gb-gplus-sharePatent US4348644 - Power amplifying circuit with changing means for supply voltage
