The present invention is directed to a road condition estimation apparatus for estimating a road condition for use in a vehicle having steering control unit for actuating a device mechanically independent of a manually operated steering member to steer each wheel. That method comprises forming a metal oxide layer on a substrate, converting at least part of the metal oxide layer to a metal layer; and oxidizing the metal layer to generate a metal oxide high-k gate dielectric layer. The controlled current sink is operably coupled to the input terminal, and is operable to controllably take up a current from the input terminal according to a transmission signal.