| 摘要 |
PURPOSE:To make it possible to have uniform photosensitivity by dividing a light receiving part into two parts and adding a bias circuit, a differential circuit, a current-voltage conversion circuit, and a current adding circuit. CONSTITUTION:When standard voltage (standard voltage of a differential circuit block 23) is set to voltage 15V0=IP1.4XRL=VREF by photoelectric currents at the time of lambda=1.4mum or thereabouts having the maximum sensitivity of Ge, the differential circuit output voltage 13 shows Vdif0.9. This voltage is returned to currents Idif0.9 which are determined by load resistance RS, and composite currents IP=IP0.9 with photoelectric currents IP0.9 from the other photodiode 22 are let flow. In the similar constitution, it operates so that they may become the same IP to the light of different wave length as well. As the difference amounts to V0=VREF are always output as voltage, by making the voltage 13 and the compensating current I correspond to each other, IP can be made constant at all times. Hereby, a light receiving circuit 5 which has uniform photoelectric currents, that is, uniform light receiving sensitivity up to the wave length with which the differential circuit can operate becomes possible. |
