use Class C amplifiers (as used in FM analogue systems) albeit with an increased dynamic range (lowest to highest output power). These power amplifiers could be/can be up to 55% efficient. All other evolving technology options including evolved variants of GSM (EDGE) have used/use a combination of phase and amplitude modulation to modulate the signal envelope. This requirement combined with a wide dynamic power control range has created a number of optimisation challenges for GSM EDGE and UMTS/LTE handsets in terms of RF power efficiency and linearity. Various techniques have been developed that take out the envelope modulation and reintroduce it after signal amplification has been achieved by the PA. These are known variously as polar modulation and/or translational loop architectures and are part of a family of post distortion and predistortion feedback and feedforward techniques that correct for amplifier nonlinearity. These techniques work well but require careful calibration or tracking of RF PA behaviour and the adaptive circuits under varying load characteristics and over temperature and time. In parallel, some of the dynamic range requirements have been reduced by implementing adaptive coding schemes and adaptive modulation schemes that will ease some of these RF PA characterisation issues. Making Telecoms Work It is therefore important to consider what technology or mix of technologies will be used in the allocated spectral band. Choosing a new nonstandard band for network deployment or failing to mandate a technology for a specific band can have major implications on both the design and function of the RFPA including cost and RF performance (efficiency and linearity). Efficiency loss translates directly into a decrease in talk time. Insufficient linearity translates into a loss of modulation accuracy at high power that will cause a loss of uplink throughput and potential interference to other users. Power amplifiers can be designed to work over large frequency ranges, for example from 150 to 2500 MHz, b