Patent ID: 8614570

Claim:
A reference current source circuit comprising: a first current mirror circuit for generating a plurality of first minute currents from a power supply voltage, the plurality of first minute currents corresponding to each other; a MOS transistor having a gate, a drain and a source, and generating an output current based on a voltage induced across the drain and the source; a gate bias voltage generator circuit comprising a plurality of first MOS transistors operating in a subthreshold saturation region based on a plurality of first minute currents selected from the plurality of first minute currents, generating a gate bias voltage so as to operate the MOS transistor in a strong-inversion linear region based on selected first minute currents, and applying the gate bias voltage to the gate of the MOS transistor; a drain bias voltage generator circuit comprising a plurality of second MOS transistors operating in the subthreshold saturation region based on a plurality of first minute currents selected from the plurality of first minute currents, generating a drain bias voltage based on selected first minute currents, and applying the drain bias voltage to the drain of the MOS transistor; and an added bias voltage generator circuit for generating an added bias voltage, which has a predetermined temperature coefficient and includes a predetermined offset voltage, based on one first minute current selected from the plurality of first minute currents, so that the output current becomes constant against temperature changes, wherein the drain bias voltage generator circuit adds the added bias voltage to the drain bias voltage, and applies a voltage of adding results to the drain of the MOS transistor as the drain bias voltage.