An LD-Driver with a back termination circuit is disclosed. The back termination circuit of the invention provides a transistor as an active device, a current source to provide a bias current to the transistor, and a resistor as a passive element that couples the transmission lines carrying a differential signal thereon. Because the transistor shows a differential resistance of several tens of ohms by providing only a few milli-amperes, the output impedance of the LD-Driver may be substantially matched with the characteristic impedance of the transmission line with lesser additional power consumption.