| 摘要 |
PURPOSE:To obtain stable photo output, by installing a current-voltage conversion circuit and a peak value detecting circuit which detects the peak value of the output voltage of the conversion circuit, between the anode of semiconductor laser and the earth. CONSTITUTION:When the pulse signal voltage is not impressed, the current determined by the bias current controlling voltage flows through the semiconductor laser diode 3. The potential of one end point P of the resistor R4 descends, and the condenser C5 is charged by the current flowing through the diode D5, whose potential becomes equal to that of the point P. When the pulse signal voltage is impressed and becomes 'H', the potential of the point P descends furthermore, and the voltage of the condenser C5 also descends. When the pulse signal voltage turns to 'L', the potential of the point P ascends, and the diode D5 turns OFF. If the resistance value of R4 is sufficiently large, the voltage of the capacitor C5 is maintained, and the detected peak value is output form the terminal Q as the peak value. By selecting adequately the time constant C5R5, the peak value of laser current can be detected independently of the mark ratio of the pulse signal. |
