| 摘要 |
PURPOSE:To prolong the life of a power source such as a battery or the like by constituting the circuit so that it can operate at a low source voltage. CONSTITUTION:A photodiode 32 is connected between an inversive input terminal and a non-inversive input terminal of an operational amplifier 31, and the inversive input terminal is connected through a diode 33 to an output terminal and a constant voltage is applied to the non-inversive input terminal. The output terminal of the operational amplifier 31 is connected through a diode 34 to the non-inversive input terminal of an operational amplifier 35, and an output signal is led out from the output terminal 36 of operational amplifier 35. When a light beam 37 is incident on the photodiode 32, a photocurrent IP corresponding to the intensity of the light beam flows through the diode 33. A constant current IK flows through the diode 34. The output voltage obtained at the output terminal 36 becomes one in which the photocurrent IP has been logarithmically converted. |
