Non-volatile semiconductor memory device equipped with high-speed sense amplifier unit

A non-volatile semiconductor memory device fabricated on a single semiconductor chip, comprising:

• a) a plurality of memory cells each selectively entering first and second states for changing the amount of current passing therethrough;
• b) a selecting means for selecting one of said plurality of memory cells;
• c) a sense amplifier unit for producing an output voltage level indicative of one of said first and second states, and having an input node coupled with said one of said plurality Of memory cells, a gate means shifted between on and off states depending upon the state of said one of said plurality of memory cells for controlling a current path between said input node and an output node, a current supplying circuit for controlling the amount of current supplied from a first source of voltage level to said output node, and a make-up circuit having a current mirror configuration for constantly supplementing current to said output node until said output node reaches a predetermined voltage level as high as said first source of voltage level regardless of voltage fluctuation of said first source, said gate means comprising a gate transistor coupled between said input node and said output node of said sense amplifier unit, and an inverting circuit having an input node coupled with said input node of said sense amplifier unit and an output node coupled with a gate electrode of said gate transistor, said current supplying circuit comprising a parallel combination of a first n-channel enhancement type field effect transistor and a first p-channel enhancement type field effect transistor coupled between said first source of voltage level and said output node of said sense amplifier unit, a gate electrode of said first n-channel enhancement type field effect transistor being coupled with said first source of voltage level, a gate electrode of said first p-channel enhancement type field effect transistor being coupled with said output node of said sense amplifier unit;
• d) a reference unit for producing a reference voltage level at an output node thereof;
• and
• e) a comparator means having a first input node coupled with said output node of said sense amplifier unit and a second input node coupled with said output node of said reference unit, and operative to compare the output voltage level with said reference voltage level for producing an output voltage signal indicative of said one of said first and second states.