The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 23, 2008
Filed:
Oct. 31, 2006
Kohichiroh Sugimoto, Tenri, JP;
Kohichiroh Sugimoto, Tenri, JP;
Sharp Kabushiki Kaisha, Osaka-shi, JP;
Abstract
A light-receiving amplifier circuit of the present invention includes: a first preamplifier circuit to which a light-receiving element is connected; a second preamplifier circuit which is the same type as the first preamplifier circuit and which is apart from the light-receiving element; and a differential amplifier circuit for amplifying output voltage differential between the preamplifier circuits, wherein each of the first preamplifier circuit includes an amplifier and first and second plural feedback resistors, each of which resistors has an end commonly connected to an input terminal of the amplifier; an amplification factor of the differential amplifier circuit is less than one; and the first preamplifier circuit includes an output voltage expanding circuit which is connected to (i) another end of the first feedback resistors in the first preamplifier circuit and (ii) an output terminal of the amplifier, and which circuit is for expanding an output voltage range from the amplifier and supplying the expanded output voltage range to the differential amplifier circuit. This configuration provides a light-receiving circuit which is capable of reducing heat noise to prevent deterioration of the S/N ratio, while avoiding narrowing down of an output voltage range.