Patent ID: 8004265

Claim:
A voltage generating circuit for generating a first reference voltage and a second reference voltage with a voltage difference, comprising: a constant current source; a ground point; a first resistor, coupled to said constant current source, for generating said first reference voltage at a first voltage output end located at a first point between said first resistor and said constant current source; a second resistor, coupled between said first resistor and said ground point, for generating said second reference voltage at a first voltage output end located at a second point between said first resistor and said second resistor; and a first controlled switch, connected in parallel to said second resistor for determining the first and second reference voltage; wherein said first resistor and said second resistor are connected in series between said constant current source and said ground point, and said voltage difference is fixed between said first reference voltage and said second reference voltage regardless of the state of the first controlled switch.