The article introduces several configurations of class E power amplifiers in CMOS technologies. Each configuration, however, alleviates some problems in the design of class E power amplifiers. The two-stage class E power amplifier reveals the design technique for the driving stage, which provides a more efficient driving signal in terms of class E operation. The complementary configuration takes advantage of the symmetrical circuit topology, which allows much lower total harmonic distortion in the output signal. The power-adaptive technique based on high-Q varactors gives a more feasible and effective approach to achieving the function of output power control for switching-mode power amplifiers. An approach to implement linear power amplification using switching mode power amplifiers is also introduced that can achieve linear amplification while still keeping high power efficiency and output power.