Patent ID: 7382306

Claim:
An AD converter comprising: a reference voltage generator circuit having a plurality of resistors connected in series with a predetermined reference voltage applied to both ends thereof, said reference voltage being divided at connecting points between respective ones of said plurality of resistors to generate a plurality of reference voltages; a voltage comparator circuit configured to compare said plurality of reference voltages and analog input signals for conversion into predetermined comparison output signals; and a variable voltage circuit connected to a connecting point of said reference voltage generator circuit and provided with a control signal input terminal inputted with control signals, configured to set an output voltage to be outputted to said connecting point at a first predetermined value based on said control signals, wherein said output voltage of said variable voltage circuit is varied, so that a ratio of a potential difference between said connecting point connected with said variable voltage circuit and said connecting point juxtaposed, on a higher potential side, to said connecting point, to a potential difference between said connecting point connected with said variable voltage circuit and said connecting point juxtaposed, on a lower potential side, to said connecting point, is varied to a second predetermined value.