A 1.9-GHz CMOS power amplifier for polar transmitters was implemented with a 0.25-mu m radio frequency CMOS process. All the matching components, including the input and output transformers, were fully integrated. The concepts of mode locking and adaptive load were applied in order to increase the efficiency and dynamic range of the amplifier. The amplifier achieved a drain efficiency of 33% at a maximum output power of 28 dBm. The measured dynamic range was 34 dB for a supply voltage that ranged from 0.7 to 3.3 V. The measured improvement of the low power efficiency was 140% at an output power of 16 dBm.