Matsushita Electronics Corporation

Katuhiko Oimura

Hideaki Usukubo

Katuichi Oosawa

This invention provides an improved photodetector with the availability of various amplifiers and with a small circuit scale. A first light-receiving element PD.sub.1 is composed of a first impurity region of the n-type formed on a p-type semiconductor substrate and a second impurity region of the p-type formed at a surface zone of the first impurity region. A second light-receiving element PD.sub.2 is composed of the semiconductor substrate and a third impurity region of the n-type. PD.sub.1 and PD.sub.2 are connected together in series. Such arrangement makes it possible to reduce the circuit scale of photodetectors if a bipolar transistor or the like is used as an amplifier means. The photosensitivity becomes higher since reverse-bias voltages are applied to PD.sub.1 and PD.sub.2. Additionally, it is possible to set a wavelength band for light to be detected, according to the area ratio of PD.sub.1 and PD.sub.2.

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Shiga, Japan

Katuhiko Oimura