Architectures for Efficiency Enhancement in Power Amplifiers

In this paper, a comparative study of different efficiency enhancement architectures for power amplifiers (PA) has been undertaken. Architectures such as Doherty, Outphasing and Envelope tracking have been discussed in this paper. These architectures can be used individually or a combination of these can be used. The Doherty power amplifier (DPA) is one of the most regularly utilized power amplifier topologies in cellular systems. The advantages of Doherty architecture are the flexibility and simple design, whereas the disadvantages include the inherent bandwidth restrictions because of the use of narrow-band quarter-wavelength transmission lines for impedance transformation. The outphasing method provides good efficiency, but branch loading creates a problem. The Envelope tracking (ET) approach uses drain-bias modulation to amplify a modulated signal with a high peak-to-average power ratio (PAPR). To achieve flawless envelope tracking, the supply control signal and the radio frequency (RF) input envelope should be time-matched.