Energy efficiency has become almost as critical for 5G equipment as performance and costs, changing the balance of concern between them. Operators as well as their equipment suppliers have to meet targets for carbon emissions that have put the spotlight on the RAN as a major and growing contributor to the overall telco electricity budget. The telecoms sector as a whole accounts for 1.5% of total global electricity consumption, not so far below the 2% of the much-vilified aviation sector. The RAN accounts for an increasing proportion of this and while there has been growing emphasis on sleep modes and techniques for reducing wasted power consumption primarily as heat, the spotlight is falling most on the power amplifiers (PAs) that…