| 摘要 |
PURPOSE:To enable to detect a small photocurrent stably at a preferable S/N ratio by integrally forming a photoelectric converter and an amplifier, providing an insulated gate type transistor at the input stage of the amplifier and inputting the output of a photoelectric converter to the gate electrode. CONSTITUTION:When a light L is incident on a photodiode 1, a photocurrent corresponding to the intensity of the incident light L flows to the photodiode 1. This photocurrent is logarithmically compressed by a logarithmic converter which has an operational amplifier 2 and a transistor 3, and output from an output terminal 23 as an output voltage V0. Since the input stage has thus MOS transistors 24 and 25, the light L of 10<-3> lux is incident, and even if small photocurrent of approx. 10<-12> amperes flows, a high impedance input with less leakage current is provided to obtain a stable output having preferable S/N ratio. |
