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We demonstrate a new linearized monolithic microwave integrated circuit smart power amplifier of extraordinary high power-added efficiency (PAE), especially at the most probable transmission power of wide-band code-division multiple-access handsets. A PAE of 21% at 16 dBm of output power, which is the maximum bound of the most probable transmission power in IS-95 systems, was obtained, as well as 40% at 28 dBm, the required maximum output power, with a single-chip MMIC power amplifier. The power amplifier has been devised with two InGaP-GaAs heterojunction bipolar transistor amplifying chains parallel connected, each chain being optimized for a different P1dB (1-dB compression point) value: one for 16 dBm for the low-power mode, targeting the most probable transmission power, and the other for 28 dBm for the high-power mode. The high-power mode operation shows 40% of PAE and -30 dBc of adjacent channel leakage power ratio (ACLR) at the maximum output power of 28 dBm. The low-power mode operation exhibits -34 dBc of ACLR at 16 dBm with 14 mA of a quiescent current. This amplifier improves power usage efficiency and, consequently, the battery lifetime of the handset by a factor of three.