A memory device that includes a first memory cell, a second memory cell and a sense amplifier. The sense amplifier includes a first branch and a second branch and are configured to output a first voltage and a second voltage to the first memory and the second memory, respectively in a trimming operation. A first clamp device of the sense amplifier includes a first clamp transistor and a plurality of first trimming transistors that are coupled to the first clamp transistor in parallel. The gate terminals of the first clamp transistor and the plurality of first trimming transistors are biased by a fixed clamp voltage. Each of the plurality of first trimming transistors is selectively conducted to compensate a mismatch between the first voltage and the second voltage.