42% high-efficiency two-stage HBT power-amplifier MMIC for W-CDMA cellularphone systems

This is the first paper to report on a high-efficiency two-stage heterojunc tion-bipolar-transistor power-amplifier monolithic microwave integrated cir cuit (MMIC) for 1.95-GHz wide-band code-division multiple-access (W-CDMA) c ellular phone systems. Power amplifiers for W-CDMA systems are required to operate at high efficiency and high linearity over a wide range of output p ower levels. To obtain high efficiency at low output power (P-out) as well as at the required maximum P-out, and obtain a high linearity at the maximu m P-out, we chose near-class-B operation. To improve linearity at a medium P-out range, we suppressed the gain distortion resulting from near-class-B operation by using an adaptive biasing technique. The MMIC exhibited a powe r-added efficiency of 42%, the highest ever reported, a gain of 30.5 dB, an d an adjacent channel leakage power ratio at a 5-MHz offset frequency of -3 8 dBc at a P-out of 27 dBm under a supply voltage of 3.5 V with 3.84-Mcps h ybrid phase-shift keying modulation.