Patent ID: 8897652

Claim:
An optical transmission circuit, comprising: a light emitting element; and a differential amplifier circuit to which differential input signals are input to modulate an optical output of the light emitting element, wherein the differential amplifier circuit includes a first current source having a first end and a second end, the first end being connected to a first potential source, a first transistor having a first source, a first drain, and a first gate, the first source being connected to the second end, one of the differential input signals being supplied to the first gate, a second transistor having a second source, a second drain, and a second gate, the second source being connected to the second end, another one of the differential input signals being supplied to the second gate, a third transistor having a third source, a third drain, and a third gate, the third gate and the third drain being connected to the first drain, the third source being connected to a second potential source, a fourth transistor having a fourth source, a fourth drain, and a fourth gate, the fourth gate and the fourth drain being connected to the second drain, the fourth source being connected to the second potential source, a second current source having a third end and a fourth end, the third end being connected to a third potential source, and the fourth end being connected to the second drain, and a fifth transistor having a fifth source, a fifth drain, and a fifth gate, the fifth gate being connected to the fourth gate, the fifth source being connected to the second potential source and the fifth drain being connected to the light emitting element, and wherein the light emitting element is disposed between a fourth potential source and the fifth drain, and a potential of the fourth potential source is higher than potentials of the first and third potential sources which are equal.