A power amplifier having a first stage amplifier and a second stage amplifier, each stage of the power amplifier being configured in one of at least two power states based on a desired power output. When the first and second stages are configured in a first state, the power amplifier delivers efficient...http://www.google.de/patents/US6791407?utm_source=gb-gplus-sharePatent US6791407 - Switchable power amplifier
