A memory device in accordance with embodiments of the present invention includes a reference cell array and a plurality of banks. Each of the banks includes memory cells. A plurality of current copier circuits corresponds to the banks, respectively. Each of the current copier circuits copies a reference current flowing through a reference cell array to generate a reference voltage. A plurality of sense blocks correspond to the banks, respectively. Each of the sense blocks includes a plurality of sense amplifiers for sensing data from a corresponding bank in response to the reference voltage from the corresponding current copier circuit. Memory cell lay-out area is reduced, and sense speed is increased.