Nonvolatile memory devices and methods of driving the same

A method of driving a nonvolatile memory device, the method comprising:

• reading a first reset current in a first cycle;
• applying a first set voltage to a unit memory cell and reading a set current in a second cycle immediately following the first cycle;
• comparing the set current to the first reset current;
• applying a second set voltage to the unit memory cell if a difference between the set current and the first reset current is less than a minimum value;
• and
• applying a first reset voltage and a third set voltage sequentially to the unit memory cell if the difference is greater than a maximum value.

A nonvolatile memory device, comprising:

• a memory cell array including a plurality of unit memory cells arranged in a matrix shape including rows and columns;
• a row decoder configured to sequentially activate the unit memory cells of the memory cell array one row at a time;
• a column decoder configured to sequentially activate the unit memory cells of the memory cell array one column at a time;
• a sense amplifier configured to amplify current values output from the column decoder;
• a buffer configured to store a first current value of a first cycle, the first current value being amplified in the sense amplifier;
• a comparator configured to compare the first current value to a second current value of a second cycle immediately following the first cycle, the second current value output from the sense amplifier;
• a write circuit configured to apply set and reset signals to the unit memory cells activated by the row decoder and the column decoder;
• and
• a control circuit configured to control operations of the buffer, the comparator, and the write circuit.