A power efficient W-CDMA smart power amplifier with emitter area adjusted for output power levels

We demonstrate a power efficient HBT MMIC smart power amplifier to provide improved power efficiency for W-CDMA mobile terminals. A small part of amplifier transistors is activated selectively to deliver output power with improved efficiency for low power mode of 16 dBm, and the PAE (power added efficiency) is increased by a factor of 1.8 using 21 mA of a quiescent current. At a high power mode, the MMIC reveals 27 dBm output power with the PAE of 33.4%. From this approach the battery lifetime can be extended as much as 2.5 times through calculating overall average power usage efficiency. The fabricated chip size is as small as 0.95/spl times/1 mm/sup 2/ including input/inter-stage matching network and all active bias circuits.