Mixed-signal Doherty power amplifiers in CMOS

There is an increasing interest to explore novel Doherty power amplifier (PA) architectures by utilizing digitally intensive architectures, i.e., RF power DACs, and mixed-signal techniques. In this paper, we will first review recent mixed-signal PA development. We will then present two mixed-signal Doherty PAs in CMOS. These digitally intensive designs enable precise controls of the Doherty main/auxiliary amplifiers to achieve optimum active load modulation for back-off efficiency enhancement. Moreover, the reprogramming nature of these mixed-signal Doherty PAs allows linearity enhancement and robust Doherty operations under antenna impedance variations. In addition, these mixed-signal PAs offer unique flexibility and allow hybrid integration with other PA techniques, e.g., Class-G operation, for further efficiency and linearity enhancement.