This paper presents a 2-phase 3-level (2P3L) envelope tracking supply modulator (ETSM) for a 20 MHz LTE RF power amplifier (PA) as a solution for the envelope tracking (ET) system. This 2P3L ETSM that is composed of only switching converters achieves high efficiency, fast transient response, and a small output current ripple. To properly operate the proposed 2P3L ETSM, 4 PWM signals with a 90° phase shift from each PWM signal are required without any mismatch between duty cycles. To remove the mismatch, a time-division multiplexing comparator (TDMC) and a duty-cycle calibrator (DCC) are proposed. Thanks to the proposed techniques, the proposed ETSM fabricated in 0.18 μm CMOS achieved the highest peak dynamic efficiency of 88.6% with a LTE20 signal, which is superior to the state-of-the-art systems.