Energy efficiency of RF Frontends (RFFE), especially transmitters, continues to gain greater prominence. Meeting the efficiency challenge is increasingly difficult at higher operating frequencies and bandwidths, such as those proposed for 5G. The document focusses on devices for the 3.5 GHz NR (5G New Radio) candidate band, but its findings are equally applicable to developments and measurements for, for example, K-band satellite applications or mmW NR candidate bands, where efficiency is an even more crucial design target.