Patent ID: 6195288
Filing Date: 2001-02-27
Classification: G11C

Abstract:
A nonvolatile semiconductor memory device in which,based on a voltage difference between a voltage which corresponds to a data storage state of a memory cell and a voltage which corresponds to a pseudo-data storage state of a reference cell, data stored in said memory cell is readout, said nonvolatile semiconductor memory device comprising:said reference cell which comprises a first reference cell held in a state where said pseudo-data is written therein and a second reference cell held in a state where said pseudo-data is erased therefrom,a first driving transistor which is turned ON by a signal for reading out said data, to supply a current to said memory cell;a second driving transistor and a third driving transistor which have same construction and characteristics as said first driving transistor and also which are turned ON by said signal, to supply a current to said first and second reference cells respectively; anda sense-amplifier which has a first input terminal supplied with an output voltage of said first driving transistor a second input terminal supplied with an average of an output voltage of said second driving transistor and an output voltage of said third driving transistor, in order to detect said voltage difference.