| 摘要 |
PURPOSE:To increase the feedback resistance value in case the optical input is small and decrease the resistance value when the input is large respectively, thus securing a high S/N for the small input as well as minimizing occurrence of the output saturation at the input time. CONSTITUTION:Amplifier 11 consists of input impedance 12 and equivalent voltage source 13 representing the output, and the feedback resistance is produced by control-type variable resistance 14. And the value of the resistance is varied by the input given from control terminal 15. Therefore, the feedback resistance value increases when the optical input os small to decrease the feedback quantity. Thus the deterioration of S/N due to the feedback resistance is reduced. While in case the optical input is large, the feedback resistance decreases to reduce the input impedance of the amplifier. As a result, the saturation of the output is not caused easily, thus giving deterioration to the dynamic range of the input light. |
