A laser driver comprises a PNP transistor current source, an inductor
coupled to the PNP transistor current source, a switch coupled to the
inductor, and a current sink coupled to the switch. The PNP transistor
current source supplies a first current to a laser if the switch is
closed and a second current to the laser if the switch is open. The PNP
transistor current source, inductor, switch, and current sink are on a
single semiconductor chip.