Flash memory

The flash memory cell consists of one transistor with a floating gate. Threshold voltage of this gate can be programmed by applying an electric field. Transistor is the memory cell with two states corresponding to the existence of charges (electrons) at the floating gate. In NOR flash memory cell, F-N tunneling mechanism for the erase operation and the hot electron injection mechanism for the programming operation. In NAND flash memory cell, F-N tunneling mechanism is used for the erase operation. In flash memory circuit, charge-pump mechanism is implemented with n-MOS or p-MOS transistors for the generation of a high positive or a negative voltage. The charge-pump circuit consists of a chain of the diode and capacitors which are discharged successfully after each half-clock cycle.