Patent ID: 8716959

Claim:
A device comprising: a coil driver to drive a coil that,-hen driven, effects a linear displacement of a motion device having a magnet; a magnetic field sensor to detect a magnetic field associated with the linear displacement and to produce an output signal in response thereto; and an interface, responsive to requests provided by an external controller and corresponding to desired linear displacements of the motion device, to receive a request as a first input and the magnetic field sensor output signal as a second input, and to produce an input signal to the coil driver having a level indicative of a relationship of the second input with respect to the first input wherein the interface comprises a first difference amplifier comprising a first port configured to receive the first input, a second port configured to receive the second input and a third port to provide an output of the first difference amplifier, wherein the interface further comprises a second difference amplifier comprising a first port configured to receive the output of the first difference amplifier and a second port configured to provide the input signal to the coil driver, and wherein the second difference amplifier further comprises a third port coupled to the coil driver and coupled to ground through a sense resistor.