A 3.3V supply single-voltage AlGaAs/InGaAs PHEMT with double channels has been developed for CDMA handsets for global mobile personal communication systems. The PHEMT has an output power of 24.2dBm (75.2mW/mm output power density), 37% power-added efficiency. and a third-order intermodulation distortion Im el of -30.7dBc under single-voltage operation with a 3.3V drain voltage and 1.6GHz frequency. The power density is the highest among those reported for poser devices operating at a single voltage. The good performance is obtained by incorporating an AlGaAs/GaAs quantum well channel between the gate and the InGaAs channel.