In this overview article, the effective capabilities of power amplifiers and wireless transmitters operating under supply modulation will be addressed. Special attention will be paid to: (i) identification of the circuit and system level limiting factors, (ii) possible ways of overcoming them, and (iii) analysis and implementation of one CDMA2000 polar transmitter. This is believed to offer the reader a comprehensive understanding of the overall transmitter behavior and of the underlying constraints that must be accounted for.