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:
Apr. 13, 1999
Filed:
Oct. 29, 1997
Masayoshi Ohkawa, Tokyo, JP;
Toshio Takeshima, Tokyo, JP;
NEC Corporation, Tokyo, JP;
Abstract
A variation in threshold of a memory cell is detected at a higher speed. A multi-valued nonvolatile semiconductor memory has a nonvolatile memory cell 41 for storing n-values (n.gtoreq.3) of data as thresholds in one cell, a reference signal generator 44 for emitting a reference signal group Vri (i.ltoreq.(n-1)), a reference signal group VriH(=Vri+.DELTA.V) and a reference signal group VriL(=Vri-.DELTA.V), a differential amplifier 43 for receiving either one of signals Vci (Vci<VriL<Vri<VriH<Vc(i+1)) corresponding to the stored data in the memory cell 41 at one input terminal and receiving the reference signal groups Vri, VriH or VriL at the other input terminal, a latch circuit 46 for latching output of the differential amplifier 43, a comparator 47 for comparing the output of the differential amplifier 43 with the output of the latch circuit 46, and a controller 48 for emitting control signals D1 to D6 in accordance with the output of the latch circuit 46 and controlling the differential amplifier 43 and the comparator 47.