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. 01, 1998
Filed:
Feb. 21, 1997
Naoki Nishiyama, Yokohama, JP;
Sumitomo Electric Industries, Ltd., Osaka, JP;
Abstract
The photocurrent generated by a photodiode receiving light substantially flows through a feedback resistor when the incident light intensity is low. As the incident light intensity increases, the source and drain of a FET connected in parallel to the feedback resistor establish a conducting state therebetween, whereby the photocurrent is divided into a current flowing through the feedback resistor and a current flowing through the FET connected in parallel to the feedback resistor. Accordingly, transimpedance is equivalently lowered, while the feedback resistor is restrained from lowering the output potential. When the incident light intensity is further increased, a gate bias current flows into the gate of an input-stage FET of an amplifier, whereby the photocurrent is divided into the current flowing through the feedback resistor, the current flowing through the FET connected in parallel to the feedback resistor, and the gate bias current. Accordingly, the preamplifier can operate even under a larger optical input. Thus realized is a novel configuration of a preamplifier for optical communication, from which a stable operation is expected even when the power supply voltage is lowered and which can operate at a single power source voltage as well.