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. 05, 2000
Filed:
Mar. 24, 1999
Atsuo Fukui, Chiba, JP;
Seiko Instruments Inc., , JP;
Abstract
To eliminate the offset voltage of a differential amplifier and ensure stable operation even when an input voltage is zero, a settable constant current source and a level shifting circuit are connected to at least one of the non-inverted and inverted input terminals of a differential amplifier. The constant current source produces a constant current that is set according to the offset voltage of the differential amplifier. In one embodiment, the level shifting circuit comprises a pair of depletion mode P-MOS transistors each connected in series to a settable constant current source, the respective series-connected pairs being connected to each input of the differential amplifier. The constant current source has a constant current value that may be varied by trimming using a laser or the like. By setting the output voltages of each such circuit equal, the offset voltage of the differential amplifier is eliminated.