Patent ID: 7542400

Claim:
A laser diode (LD) driver driving two or more LDs by receiving different sets of channel control signals corresponding to each of the LDs, where the channel control signals control the power levels of a laser signal of the respective LD, the LD driver comprising: switches turning on and off driving potentials of the LD corresponding to one of the sets of channel control signals, the driving potentials corresponding to the power levels of the laser signal of the LD corresponding to the one of the set of channel control signals; a multiplexer multiplexing the driving potentials and outputting a multiplexed signal; a switch that is driven by an LD selection signal and selectively outputs the multiplexed signal from the multiplexer to drive one of the LDs; a monitor diode monitoring the power level of the laser signal and outputting a monitor signal; a sample and hold unit sampling and holding the monitor signal and outputting a signal indicative of the held monitor signal; a differential amplifier calculating a difference between a reference signal corresponding to the power level of the laser signal and the output signal from the sample and hold unit; and an adder that is disposed between the multiplexer and the switch, driven by the LD selection signal to add the difference and the multiplexed signal, and outputs the added result to the switch driven by the LD selection signal.