Patent ID: 7652664

Claim:
A light emitting device comprising: a light emitting element, a bipolar transistor, an operational amplifier, a driver circuit, a first resistor, a second resistor, a third resistor, and a fourth resistor, wherein the bipolar transistor has a base terminal connected to an output terminal of the operational amplifier and a collector terminal connected to a low power potential, wherein the first resistor has one terminal connected to a first high power potential and the other terminal connected to a first input terminal of the operational amplifier, wherein the second resistor has one terminal connected to the first input terminal of the operational amplifier and the other terminal connected to the emitter terminal of the bipolar transistor, wherein the third resistor has one terminal connected to a second high power potential and the other terminal connected to a second input terminal of the operational amplifier, wherein the fourth resistor has one terminal connected to a second input terminal of the operational amplifier and the other terminal connected to a low power potential, wherein a potential from the emitter terminal of the bipolar transistor and the other terminal of the second resistor is supplied as a low power potential of a buffer of the driver circuit, and wherein the second high power potential is supplied as a high power potential of the buffer.