Patent ID: 7317441

Claim:
A drive circuit providing an output voltage in accordance with an input voltage comprising: a first transistor connected between a first power supply node and an output node; a constant current circuit connected between said output node and a second power supply node; and an offset compensating circuit compensating for an offset voltage occurring depending on a threshold voltage of said first transistor, wherein said offset compensating circuit holds said offset voltage, and provides a first voltage produced by shifting said input voltage by said held offset voltage to a gate electrode of said first transistor; said constant current circuit includes; a second transistor connected between said output node and said second power supply node, and a first voltage holding circuit holding a second voltage determined depending on a threshold voltage of said second transistor and provided for turning on said second transistor; said second transistor receives on its gate electrode said second voltage, and passes a constant current through said first transistor connected to said output node; and said first transistor receives on its gate electrode said first voltage provided from said offset compensating circuit, and provides an output voltage at the same potential as said input voltage to said output node.