I'm building a system to steer an automobile automatically down the center of a highway lane. I'm currently testing a sensor network for the system. I'm using 12 VDC input to the sensor network and getting an output of 1/2 VDC to 2 VDC when the car moves off-center of the lane. When the car is centered in the lane the sensor network output is around zero. I need an electronic circuit that will take that one half volt to two volt DC signal and will drive a 12 volt DC steering motor. Precisely, I need for the motor to turn one direction in the absence of a a signal and the opposite direction in the presence of the signal. Additionally. It would be better if the circuit responded to a voltage differential rather than an absolute voltage due to the problem of the zero point shifting around. Also, the sensor network can supply less than one ma. current so I need a circuit with high impedance input.