| 摘要 |
PURPOSE:To control a photo output at a constant value as well as to make possible a high-speed operation by a method wherein an input voltage proportioned to the difference current between a photovoltaic current and a reference current and a reference voltage are inputted in a differential amplifier and a forward current which is fed to a laser diode to be driven is controlled by an output which is proportioned to the difference. CONSTITUTION:When a forward current if which is fed from a current source 2 for bias reaches a threshold current, lasing takes place and a photo output Po is produced and after this, the photo output Po is augmented in proportion to the forward current If. A reference voltage Vref=0 is set in a differential amplifier 5, a voltage proportioned to the difference current between an photovoltaic current Is produced in a photo diode PD and a reference current Iref is inputted in the differential amplifier 5 and an output current Io is produced in the output line. A forward current which is fed to a laser diode to be driven from the current source for bias is controlled by this output and the photo output of the laser diode to be driven is controlled at a constant value. Thereby, with a high-speed operating property obtained, the reduction of cost can be contrived. |
