Comparative efficiency analysis of dynamically supplied power amplifiers (PA)

Data throughput, reliability, bit-error rates (BER), and backward compatibility complicate modern protocols so much that power amplifiers (PA) drive and demand most of the power mobile devices consume. As a result, PA power efficiency often limits battery life, which is why dynamically adaptive supplies are popular today. Justifying one supply scheme over another in terms of efficiency, however, is not straightforward. This paper analyzes the fundamental loss mechanisms in PAs to compare how power- and envelope-tracking (PT and ET) supplies improve efficiency. Results show that, even when ET supply efficiencies are 20% worse than PT´s, ET schemes are 4% - 29% more efficient than PT systems for CDMA IS95 (and UMTS), CDMA 2000, and 802.11 a/g protocols across input power, and better in newer protocols where peak-average ratios (PAR) are higher. In fact, envelope elimination and restoration (EER) with a dynamic supply and feedback is optimal with 29% - 35% more efficiency than Class-A ET because a nonlinear PA dissipates little conduction power, the smart supply loses less power than the nonlinear PA saves, and feedback corrects nonlinear errors.