| 摘要 |
PURPOSE:To form a highly sensitive photodetector and a current voltage conversion amplification circuit that exhibits the excellent S/N and stability in the same device, by mounting a P-type layer at the surface of an N-type epitaxial layer and by constructing the photodetector where PN photodiodes are connected in parallel after short-circuiting electrically a distance between the P-type layer and the P-type semiconductor substrate. CONSTITUTION:An N-type epitaxial layer 402 is provided on a P-type semiconductor substrate 401 and active and passive elements are formed by diffusing impurities to the N-type epitaxial layer 402. In such a semiconductor, the P-type layer 405 is prepared at the surface of the N-type epitaxial layer 402 and further, a photodetector where PN photodiodes PD1 and PD2 are connected in parallel is constructed by short-circuiting electrically a distance between the P-type layer 405 and P-type semiconductor substrate 401. For example, an anode terminal 410 of a PD2 13 is earthed and a common cathode 411 for the PD1 12 and PD2 13 are inputted in a base terminal 413 of an NPN transistor 14. Thus adequate values are selected for resistances 15 and 16 and it follows that the NPN transistor 14 is in an appropriate bias state. |
