Patent ID: 7492193

Claim:
A driver circuit comprising: a buffer circuit that performs input signal clamping by first semiconductor devices each having a nonlinear voltage-current characteristic, for output; and a temperature compensation circuit that controls direct currents to be passed through said first semiconductor devices based on a direct current to be passed through a second semiconductor device, said second semiconductor device having a forward voltage maintained to be constant by a reference voltage, said second semiconductor device comprising a voltage-current characteristic with a same temperature coefficient as temperature coefficients of said first semiconductor devices, said temperature compensation circuit comprising: a first current mirror having an input connected to an output of a constant current circuit of said buffer circuit; a differential amplifier having an input connected to an output of said first current mirror; a second current mirror having an input connected to an output of said differential amplifier; a third current mirror having an input connected to an output of said second current mirror and an output connected to said second semiconductor device, an input of said buffer circuit, and said differential amplifier; a capacitor connected to said differential amplifier; and a constant voltage circuit having an output terminal connected to said differential amplifier, said constant voltage circuit for generating said reference voltage, wherein a direct current to be passed through said first semiconductor devices is controlled based on a direct current obtained by adding a predetermined current to the direct current to be passed through said second semiconductor device, the predetermined current depending other than on a temperature change.