2020 Volume 17 Issue 10 Pages 20200121
This paper presents a compact implementation of a switch-linear hybrid envelope tracking supply modulator (HETSM). By combining transconductance-enhanced method and nonlinear current mirror technique in the operational transconductance amplifiers (OTAs), the proposed linear amplifier (LA) which utilizes the OTAs with class AB output stage achieves improved gain bandwidth and boosted slew-rate without increasing quiescent current. A good stability can also be attained without using any on-chip and off-chip compensation capacitors. The proposed LA facilitates the HETSM to achieve fast tracking with reduced chip area. An HETSM using the proposed LA in parallel with a hysteretic buck converter has been fabricated in 0.18-µm 1.8/5 V CMOS process with 1.24 mm2 die size. The measured results show that the HETSM is able to track a 10 MHz LTE signal accurately with less than 1.5% output error, achieving the maximum efficiency of 83% at 1W output power with 5 Ω resistive load. The HETSM can accommodate the variation of loading from 5 Ω to 20 Ω.
