A memory device includes a memory cell unit, a reference circuit, and a sense amplifier. The memory cell unit includes a memory cell. The reference circuit is configured to generate a reference current and includes a plurality of magnetic resistive elements. At least one of the magnetic resistive elements is in a high resistance state. The sense amplifier is coupled to the memory cell unit and the reference circuit and is configured to compare a current that flows through the memory cell to the reference current to sense a bit of data stored in the memory cell, to amplify a level of the sensed bit of data, and to output the amplified bit of data.