An overview of fast DC-DC converters for envelope amplifier in RF transmitters

In the last years, RF power amplifiers are taking advantage of the switched dc-dc converters to use them in several architectures that may improve the efficiency of the amplifier, keeping a good linearity. The use of linearization techniques such as Envelope Elimination and Restoration (EER) and Envelope Tracking (ET) requires a very fast dc-dc power converter to provide variable voltage supply to the power amplifier but theoretically the efficiency can be much higher than using the classical amplifiers belonging to classes A, B or AB. The purpose of this paper is to analyze the state of the art of the power converters used as envelope amplifiers in this application where a fast output voltage variation is required. The power topologies will be explored and several important parameters such as efficiency, bandwidth and output voltage range will be discussed.