I. Introduction
A radio frequency (RF) power amplifier (PA) is a sensitive circuit that requires a well-regulated voltage supply. A standalone buck regulator generates a fixed supply voltage Vreg to meet the maximum output voltage Vout required by the PA but high peak-to-average power ratio (PAPR) results in a Vreg significantly higher than the averaged Vout. Significant power loss occurs across the RF PA due to the difference between Vreg and Vout through heat dissipation, as shown in Fig. 1(a).