Patent ID: 7020169

Claim:
A laser diode driver comprising: a light-emitting circuit; a drive circuit for driving the light-emitting circuit; a bias circuit for adding a bias current to a pulse current outputted from the drive circuit; a light-receiving circuit for receiving monitoring light outputted from the light-emitting circuit; an I/V conversion circuit for subjecting an output from the light-receiving circuit to current-to-voltage conversion; a maximum-value detection circuit for detecting the maximum value of an output voltage of the I/V conversion circuit; an average-value detection circuit for detecting the average value of the output voltage of the I/V conversion circuit; a first comparator for comparing the maximum value with a first reference value to feed back the comparison result to the drive circuit; a second comparator for comparing the average value with a second reference value to feed back the comparison result to the bias circuit; and a reference value preparation circuit for generating the second reference value from the first reference value or from the maximum value detected by the maximum-value detection circuit.