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This paper presents design and linearization techniques for a highly efficient but nonlinear Class-E power amplifier (PA) applied to a dual-mode RF transmitter for W-CDMA/WiMAX systems. At first, a Class-E PA design is carried out for dual-band operation based on the proposed modified Class-E condition. Then, the envelope tracking and digital predistortion techniques are applied to linearize the Class-E PA by improving the PA AM/AM and AM/PM distortions. Consequently, the designed Class-E PA, although classified as a switching-mode PA, can act as a linear PA for diverse high peak-to-average-power-ratio (PAPR) wireless systems. The experimental results show that a quadrature modulation transmitter incorporating the presented envelope-tracking dual-band Class-E PA can simultaneously achieve high average efficiency and adjacent channel power rejection for 1.95 GHz W-CDMA and 2.6 GHz WiMAX applications.