Patent ID: 7928889

Claim:
An analog-to-digital converter which receives a first analog signal voltage and a second analog signal voltage, receives a first comparison voltage which decreases by a fixed inclination with time from a first reference voltage larger than the first analog signal voltage to a voltage smaller than the first analog signal voltage, receives a second comparison voltage which decreases by the same inclination as the first comparison voltage with time from a second reference voltage larger than the second analog signal voltage to a voltage smaller than the second analog signal voltage, counts cumulatively over first periods to acquire a first result, wherein each of the first periods is time required for the first comparison voltage to change from the first reference voltage to the same voltage as the first analog signal voltage, counts cumulatively over second periods to acquire a second result, wherein each of the second periods is time required for the second comparison voltage to change from the second reference voltage to the same voltage as the second analog signal voltage, and outputs a difference between the first result and the second result as a digital quantity.