An untethered stylus, configured to cooperate with a location sensor, includes a coil resonant circuit configured to develop an arbitrary AC voltage in response to a varying magnetic field produced by the location sensor. The coil resonant circuit includes a first capacitor and an inductive coil. A power...http://www.google.com/patents/US20080149402?utm_source=gb-gplus-sharePatent US20080149402 - UNTETHERED STYLUS EMPLOYING LOW CURRENT POWER CONVERTER
