Patent ID: 8054093

Claim:
A sensor threshold circuit that outputs a digital signal with a hysteresis characteristic, in receipt of an input from a sensor, the sensor threshold circuit comprising: a voltage comparator that digitizes an output voltage of the sensor; a sensor drive current detecting circuit that detects a sensor drive current; a sensor bias current generating circuit that generates a threshold current, wherein the magnitude of the threshold current is 1/K (where K>0) times the magnitude of the sensor drive current that has been detected by the sensor drive current detecting circuit, and wherein the threshold current is based upon the output from the voltage comparator; a threshold adjusting current generating circuit that generates a threshold adjusting current wherein the magnitude of the threshold adjusting current is 1/A (where A>0) times the magnitude of the sensor drive current that has been detected by the sensor drive current detecting circuit, wherein the threshold adjusting current generating circuit adds or subtracts the threshold adjusting current to or from the threshold current that has been generated by the sensor bias current generating circuit to generate a sensor bias current, and wherein the threshold adjusting current generating circuit supplies the sensor bias current to an output terminal of the sensor.