A sensing amplifier comprising a program cell current sensing circuit, an erase cell current sensing circuit and a latch circuit is provided. Each of the program and erase cell current sensing circuits further comprises a plurality of program/erase memory cells, a first NMOS transistor, a second NMOS transistor, a third NMOS transistor and a fourth PMOS transistor. Wherein, one of the drain/source of the first NMOS transistor is electrically coupled to both the program/erase memory cells and a gate of the third NMOS transistor to form a node. In addition, one of the drain/source of the third NMOS transistor is coupled to the latch circuit. Moreover, the program/erase memory cell provides a program/erase current to the first NMOS transistor. The latch circuit will be driven once the amount of the electric charges accumulated at the node caused by the program/erase current overcomes a threshold voltage of the third NMOS transistor.