Instruments and methods include a guide instrument mountable to at least one anchor extension to guide the positioning of an anchor in a bony segment. The structure comprises a Si:C, or SiGe:C, layer which is sandwiched between the gate insulator and a layer which is doped with impurities in order to provide a preselected workfunction. The power amplifier core includes first and second drive transistors configured in series between the voltage source and ground. The other extension of the cam arm is connected toward its outer end to an actuator, anchored at one end to the backup body and oriented at the other end to swing the cam arm about the pivot pin.