Ultraviolet erasable nonvolatile memory with current mirror circuit type sense amplifier

Claim 1

A nonvolatile memory device comprising: a plurality of memory cells of a first conductivity type for storing data, a reference cell having the same structure and the same first conductivity type as said memory cells, a sense amplifier comprising a first MIS transistor of a second conductivity type, a second MIS transistor having the same structure and the same second conductivity type as said first MIS transistor, wherein said gate and drain electrodes of said first MIS transistor are connected to a first node and said gate electrode of said second MIS transistor is connected to said first node and said drain electrode of said second MIS transistor is connected to a second node, and said reference cell is connected between said first node and a ground node, and said memory cell is connected between said second node and ground note; and a constant current source connected between said second node and ground node, wherein the current drivability of said current source has an intermediate value between a value of the current drivability in an erased state and a value of the current drivability in a programmed state.