Latest-generation cellular networks, such as Long Term Evolution (LTE), are literally pushing the envelope for power amplifier designers. Such engineers face the unenviable task of not only developing circuits that can boost highly modulated signals with minimum distortion, but do it in such a way that the conversion of bias energy to RF output power is at a maximum. These obsessions with amplifier efficiency make perfect sense when dealing with small, battery-powered mobile devices, but why apply the same stringent requirements to amplifiers mounted on a tower or in a cellular base station?

According to network providers, the future of many of these fourth-generation (4G) wireless networks depends on higher-efficiency power amplifiers. Not only does an efficient amplifier consume less power for a given output-power level, it also generates less heat, with less energy and effort required to keep the overall system running at safe thermal levels (with its implied higher reliability). Of course, with any design goal there is a point of diminishing returns but, for now (as the story on Nujira and RFMD shows), this is a time to enjoy some innovative approaches to higher power amplifier efficiency.