ABSTRACT
This chapter illustrates how to energize and power microsystems from ambient energy by reviewing system requirements, describing the state of the art in miniaturized energy-harnessing transducers, and presenting energy-harvesting supply and charger microelectronics currently under investigation and development. The cellular phone, for instance, is for the most part alert-that is, ready to receive calls—and while transmission demands milliwatts, awareness only requires microwatts, which is why radio-frequency power amplifiers are mostly in the light-to-moderate power region of operation. Of the ambient sources discusses solar energy generates the most power, followed by kinetic energy when harnessed by piezoelectric or electrostatic transducers. One last peculiarity to note is that inductors, unlike capacitors, receive or deliver energy, but do not store it statically over time; this is not a problem in conditioners because the overriding aim is to draw and deliver power—not store it, as rechargeable batteries and large capacitors would.
