Patent ID: 7084803

Claim:
An analog-digital conversion method which converts an analog signal into a digital value of a predetermined number of bits, in a plurality of sequential steps starting from higher bits, comprising: a first conversion step of comparing a predetermined reference voltage value with a reference voltage value generated by a first least significant bit voltage value and converting an analog signal into at least 1 bit; and a second conversion step of comparing a predetermined reference voltage value with a reference voltage value generated by a second least significant bit voltage value and converting an analog signal, having a bit component produced by conversion in said first conversion step removed therefrom and amplified by a predetermined gain, into at least 1 bit lower in the order than the bits produced by conversion in said first conversion step, wherein a value obtained by multiplying said first least significant bit voltage value by said predetermined gain is practically equal to a value obtained by multiplying said second least significant bit voltage value by a value obtained by raising 2 to the power of the number of bits produced by conversion in said second conversion step and having redundant bits excluded therefrom, and wherein said first least significant bit voltage value differs from said second least significant bit voltage value.