Patent ID: 7746973
Filing Date: 2010-06-29
Classification: G01R

Abstract:
1. A signal detection circuit for a magnetic sensor including an exciting coil and a detection coil, the signal detection circuit comprising: a differential amplifier to be applied with an output voltage of the detection coil at a time when a first drive signal is applied to a first terminal of the exciting coil and a second drive signal is applied to a second terminal of the exciting coil, the second drive signal being a signal inverted in polarity with respect to the first drive signal as well as intersecting the first drive signal twice or more; a comparator configured to output a digital signal being at one logic level in a period between two spike-shaped voltages adjacent to each other in an output voltage of the differential amplifier due to intersection of the first drive signal and the second drive signal; and a count circuit configured to perform a count operation in a period during which the comparator outputs the digital signal of the one logic level, the count circuit including a first counter configured to count a first clock having a predetermined frequency, a second counter configured to count a second clock being equal in frequency to and different in phase from the first clock, the second counter having the same number of bits as the number of bits of the first counter, and an adder configured to add count values of the first counter and the second counter.