A maximum power point tracking DC-DC boost converter and reconfigurable rectifier to harvest energy from ambient RF source in an auto-configurable mixed converter mode is presented. A reconfigurable rectifier with adjustable rectifier stages in the high input power range(-16dBm to -8dBm) and a boost converter with adaptive control in the low input power level range(-26dBm to -17dBm) to maximize the efficiency is proposed. The system is designed at UHF band(900MHz) to drive a load with 1V and shows a peak efficiency of 62.8% at -20dBm and 78.2% at -12dBm and it is implemented using UMC 0.18μm CMOS technology. © 2016 IEEE.