| 摘要 |
PURPOSE:To avoid the occurrence of the ringing with the junction capacity and then realize a quick reset of the photodiode to the normal state, by discharging once excessively the charged electric charge of the junction capacity of the photodiode and then giving the charging again later. CONSTITUTION:With supply of the noise signal from outside, the output of the operational amplifier OA1 has a high potential. Then the junction capacity of the photodiode PD is charged to turn the output potential of the OA1 to zero, and the output of the comparator OA2 becomes high potential. Thus the capacitor C1 is charged quickly via the transistors Q1 and Q2. As a result, the current of the Q3 increases, and the charged electric charge of the junction capacity of the PD is discharged gradually by the output current of the PD and the current of the Q3. In this case, the negative input potential of the OA1 is set lower than the positive potential, and thus the charged electric charge of the PD is discharged once and excessively. Then the charging is carried out again to the junction capacity of the PD via the D1 when the current of the Q3 becomes zero, thus obtaining the normal state. |
