| 摘要 |
PROBLEM TO BE SOLVED: To prevent influence on the operation of a photodiode by discharging a capacitor, lowering a voltage from a constant current generator and turning off a diode when peak light detection power instantaneously exceeds a threshold. SOLUTION: When a current Iav programmed beforehand is supplied from the constant current generator 11 to a point A, in a transition phase, the capacitor 12 is charged and the potential of the point A is raised. When the potential turns on the diode 15, the charging of the capacitor 12 is stopped and the current Iav is made to flow to the diode 15. In this case, when light power is supplied to a PIN photodiode 2, the current Iph is generated between a cathode 5 and an anode 3. Thus, the current Iav -Iph is made to flow out through the diode 15. When the peak light detection power instantaneously exceeds the threshold, the capacitor 12 is discharged, the voltage of the point A is lowered and the diode 15 is turned off. Thus, the operation of the photodiode 2 is not affected. |
