Fully Integrated HBT MMIC Series‐Type Extended Doherty Amplifier for W‐CDMA Handset Applications

A highly efficient linear and compactly integrated series‐type Doherty power amplifier (PA) has been developed for wideband code‐division multiple access handset applications. To overcome the size limit of a typical Doherty amplifier, all circuit elements, such as matching circuits and impedance transformers, are fully integrated into a single monolithic microwave integrated circuit (MMIC). The implemented PA shows a very low idle current of 25 mA and an excellent power‐added efficiency of 25.1% at an output power of 19 dBm by using an extended Doherty concept. Accordingly, its average current consumption was reduced by 51% and 41% in urban and suburban environments, respectively, when compared with a class‐AB PA. By adding a simple predistorter to the PA, the PA showed an adjacent channel leakage ratio better than —42 dBc over the whole output power range.