A highly-integrated Doherty amplifier for CDMA handset applications using an active phase splitter

A highly-integrated "extended" Doherty-type amplifier has been developed for code-division multiple access (CDMA) applications. In order to overcome the size limit of the Doherty amplifiers for reduced form-factor applications such as handsets, bulky input quadrature coupler and output λ/4-line transformers have been replaced with an active phase splitter and lumped-element networks, respectively. The active phase splitter provides inherent gain and isolation. All the components except for the output circuits have been integrated on a single chip with a size of 1.1 mm×1.4 mm. The measured data of the proposed Doherty amplifier showed better than -45 dBc adjacent channel power ratio (ACPR) over the entire power range, and 16% and 38% efficiencies at 16 and 28 dBm, respectively. The average current consumption calculated using urban compact disk game (CDG) usage profile was reduced from 76 mA (conventional class-AB amplifier) to 31 mA using our approach. This concept can be applied to a variety of wireless TX applications requiring small form factors and enhanced efficiencies.