Design and measurement of class EF2 power oscillator

A class EF2 power oscillator designed in standard 130 nm CMOS at 2.5 GHz frequency is presented. The oscillator relies on a direct path based on a power amplifier and a feedback path based on passive elements and an MOS varactor. Class EF2 is used to reduce voltage stress across the switch, enabling a higher output power for modern transistors with low breakdown voltage. The measurement on a class EF2 power oscillator at radio frequency (RF) is presented for the first time. The circuit achieves 17.65 dBm output power from a 2.5 V supply voltage with 27.1% DC-RF efficiency and presents a 150 MHz tuning range. The measured phase noise is -101.6 dBc/Hz at 1 MHz offset. The circuit was implemented in standard 130 nm CMOS technology and consumed a total area of 1.95 mm². To the authors´ knowledge this class EF2 power circuit has never been presented either at RF frequencies or in an integrated technology.