This paper reviewed the efficiency of CMOS class AB power amplifier topology especially in gigahertz frequencies. CMOS class AB power amplifier is a compromise between class A and class B in terms of linearity and efficiency between 50% to 78.5%. However, CMOS class AB power amplifier cannot have good linearity and efficiency simultaneously due to the breakdown in gate-oxide voltage and effects from hot carrier. The breakdown of oxide prevents optimum drain signal and the effect from hot carrier will reduce the quality of the overall PA design. Several works from year 1999 to 2019 with different topology such as multiple gated transistor, cascode, feedforward linearization, differential circuit, transformer combining method with common source harmonic termination and combination of a dual-switching transistor with a third harmonic tuning technique are discussed and the performances of the power amplifier are compared. The best three CMOS class AB power amplifier topologies were chosen in terms of high efficiency. The topologies are two stages with integrated input and interstage matching, Doherty amplifier combined with drain modulation based architectures and self-biased cascode topology that obtained power added efficiency of 45%, 43% and 42%, respectively. Key performance indicators for class AB power amplifier include frequency, power added efficiency, gain and output power are also discussed in this paper.
