A sense amplifier includes a sense amplifying unit, first and second isolation units, and first and second offset cancellation unit. The sense amplifying unit includes a first P-type metal-oxide-semiconductor (PMOS) transistor, a second PMOS transistor, a first N-type metal-oxide-semiconductor (NMOS) transistor, and a second NMOS transistor. In a layout of the sense amplifier, the first and second PMOS transistors are disposed in a central region of the sense amplifier, the first and second NMOS transistors are disposed at opposite sides of the sense amplifier from each other, the first isolation unit and the first offset cancellation unit are disposed between the first PMOS transistor and the first NMOS transistor, and the second isolation unit and the second offset cancellation unit are disposed between the second PMOS transistor and the second NMOS transistor. In other layouts, the locations of the PMOS transistors and NMOS transistors may be reversed.