| 摘要 |
PURPOSE:To eliminate an effect of the frequency characteristic of a photovoltaic current by a method wherein the frequency characteristic of the photovoltaic current generated in a photoelectric conversion means is corrected to be a leveled characteristic and thereby the frequency characteristic of a light output of a semiconductor laser is leveled. CONSTITUTION:A photoelectric conversion means 2 generates a photovoltaic current being proportional to a light output of a semiconductor laser 1 to be driven, and a voltage-current conversion means comprising Q2, OP2, R3, R4 and E1 outputs a current being proportional to an input voltage. A bias current is supplied from a constant-current source comprising Q1, OP1 and R1, and a current amplifier comprising Q3, Q4 and R2 receives as an input a current of the sum or the difference of an output current of the constant-current source, the photovoltaic current from the photoelectric conversion means 2 and the output current of the voltage-current conversion means and controls a forward current of the semiconductor laser 1 to be driven. Accordingly, the forward current of the semiconductor laser to be driven is controlled so that the current proportional to the input voltage be equal to the photovoltaic current. A frequency characteristic correcting circuit comprising C0, R5 and R6 corrects the frequency characteristic of the photovoltaic current from the photoelectric conversion means. According to this constitution, an effect of the frequency characteristic of the photovoltaic current is removed. |
