This paper presents the measured results and characterization of a fabricated power conditioning and energy storage integrated circuit for energy harvesters with on-chip maximum power point tracking (MPPT). This ultra-low power circuit employs an AC/DC-to-DC converter to be compatible with both AC and DC voltage energy harvesters, and features a wide input voltage and power range. The circuit was implemented using the AMS CMOS 0.35 µm high voltage technology and all the circuit blocks were designed using analog electronic techniques, with the transistors operating in the sub-threshold region, in order to obtain a minimum power consumption. In fact, this power conditioning circuit consumes less than 2 µW while featuring an input voltage range of ±0.5 V to ±50 V and a power range of 10 µW to 200 mW.