| 摘要 |
PROBLEM TO BE SOLVED: To provide a laser diode drive current control circuit where the effect of offset voltage component of an amplifier is suppressed. SOLUTION: A photodiode 106 monitors the output light of a laser diode 103. A gain-variable amplifier 109 outputs a difference between the voltage converted from a monitoring current Im by a current/voltage conversion amplifier 107 and the reference electric potential generated by a current/voltage conversion amplifier. The voltage difference is outputted as a monitor voltage Vm from buffer amplifier 110. An amplitude-detecting circuit 111 detects the amplitude of a monitor voltage Vm. An amplitude-detection circuit 114 detects the amplitude of data D inputted from a buffer amplifier 112, and generates a reference amplitude value. An operational amplifier 105 compares the amplitude of monitor voltage Vm to the reference amplitude voltage. A voltage/ current conversion circuit 104 controls a drive current Ip of the laser diode 103, so that the amplitude of the monitor voltage Vm approaches the reference amplitude value.
|
