An on-chip low power single-inductor dual-output DC-DC converter is proposed for battery and solar cell operating sensor network applications. By a new feed-forward control, a test chip fabricated by 190nm CMOS achieves a high efficiency of 87% at the practical load condition with a small area size of 0.75mm2 without any compensation capacitor. In addition, the fluctuation of the output voltage remains within 100mV when the input voltage changes from 1V to 2V. For a solar cell operation, 0.5V start-up is achieved with a process technology of flash-memory embedded micro-computers by utilizing forward back bias. A super capacitor is charged up to 5V from a solar cell with an implemented MPPT.