BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of semiconductor memory devices of the embodiments of the present invention.
FIG. 2 is a block diagram of a memory cell.
FIG. 3 is a block diagram of a first amplifier in Embodiments 1, 2, 3 and 4 of the present invention.
FIG. 4 is a block diagram of a switch element in Embodiments 1, 4 and 5 of the present invention.
FIG. 5 is a block diagram of a second amplifier in the embodiments of the present invention.
FIG. 6 is a timing chart showing the operation in Embodiment 1 of the present invention.
FIG. 7 is a block diagram of a switch element in Embodiment 2 of the present invention.
FIG. 8 is a timing chart showing the operation in Embodiment 2 of the present invention.
FIG. 9 is a block diagram of a switch element in Embodiment 3 of the present invention.
FIG. 10 is a timing chart showing the operation in Embodiment 3 of the present invention.
FIG. 11 is a timing chart showing the operation in Embodiment 4 of the present invention.
FIG. 12 is a block diagram of a first amplifier in Embodiment 5 of the present invention.
FIG. 13 is a timing chart showing the operation in Embodiment 5 of the present invention.
FIG. 14 is a block diagram of a conventional semiconductor memory device.
FIG. 15 is a timing chart showing the operation of the conventional semiconductor memory device.