The present invention is to provide a laser driver able to select
configurations for the high speed application and for the lower speed and
the lower power dissipation. The laser driver of the present invention
provides a pair of transistors with the differential configuration whose
outputs are complementary to each other, and a pair of load circuits
connected between respective outputs of the paired transistor and the
power supply line. Two outputs of the paired transistor are also
connected to the anode and cathode of the laser diode and two load
circuits each includes a switch to isolate the output of the transistor
from the power supply line to vary the output impedance of the laser
driver.