Nonvolatile memory devices and methods of operating the nonvolatile memory devices

A method of operating a nonvolatile memory device including a voltage generator, the method comprising:

• calculating a difference between a voltage level of a first bit line node and a voltage level of a second bit line node;
• changing a first reference voltage level of the voltage generator to a second reference voltage level based on the difference between the voltage levels of the first bit line node and the second bit line node;
• and
• determining a target voltage level based on any one of the first reference voltage level and the second reference voltage level,
• wherein the first bit line node is closer from an output terminal of the voltage generator than the second bit line node.

A nonvolatile memory device including a switch, a voltage subtractor, and a voltage adder, the nonvolatile memory device comprising:

• a memory cell array including memory cells and select word lines coupled to the memory cells;
• a control logic configured to control the voltage subtractor to calculate a difference between a voltage level of a first word line node and a voltage level of a second word line node, control the voltage adder to change a first reference voltage level to a second reference voltage level based on the difference between the voltage levels of the first word line node and the second word line node, and control the switch to determine a target voltage level based on any one of the first reference voltage level and the second reference voltage level;
• and
• a voltage generator configured to generate the target voltage level,
• wherein the first word line node and the second word line node are nodes on the selected word line, and the first word line node is closer from an output terminal of the voltage generator than the second word line node.