This paper presents a study and analysis of high efficiency CMOS power amplifier (PA) for Internet of Thing (IoT) application. The studied mainly focused on the topology employed in designing high efficiency PA in gigahertz range frequencies. This study covers the basic class-E PA and the topologies in designing class-E PA such as single-stage, two-stage, multistage and differential. The circuits structure and the performances of class-E PA is discussed. The analysis is focusing on the efficiency of the proposed PA. The latest CMOS PAs developments have been studied and a summarization of the performance specification for different topologies are elaborated.
