This letter demonstrates a high-dynamic range GaAs heterojunction bipolar transistor Class E power amplifier (PA) for a WCDMA envelope elimination and restoration transmitter using a dual-mode amplification. An impedance optimization can operate the lossless high-power Class E mode and lossless low-power Class AB mode. This PA has a high dynamic range of -50 dBm to 27 dBm and obtains a remarkably improved efficiency of 9% and 27% power-added efficiency (PAE) at output powers of 0 dBm and 10 dBm, respectively, for low-power mode, and 40% and 48% PAE at 20 and 27 dBm, respectively, for high-power mode.