Mixed-signal Doherty power amplifiers in CMOS

Abstract

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.