Amplification devices configured to amplify transmission power have heretofore been used in various electronic apparatuses including base stations in a mobile communication system. In particular, with an increase in the speed of telecommunications in recent years, there is a demand for amplifying transmission power with higher efficiency from the viewpoint of saving power consumption and the like. It is known that an amplification device achieves the highest efficiency in a power saturation state (a non-linear state). An amplification device which employs outphasing (hereinafter referred to as an “outphasing amplification device”) is proposed as an amplification device adapted to achieve such high efficiency. Examples of a combiner used in the outphasing amplification device include a Chireix combiner. The Chireix combiner has an asymmetrical configuration (transmission line (TL)=90±0 deg, for example) to improve power efficiency characteristics at an output back-off power point.
Such a technique is described, for example, in Japanese Laid-open Patent Publication No. 2007-174148.