Sense amplifier for a semiconductor memory device.

摘要

In a sense amplifier, the first input terminal of the differential amplifier (26) is connected to a first MOS transistor (23) operating as a transfer gate, a first floating gate transistor (22) operating as a memory cell, and a first load (24). The gates of the first MOS transistor (23) and the first floating gate transistor (22) are respectively connected to the column-select line (BL) and the word line (WL). The second input terminal of the differential amplifier (26) is connected to a second load (28), a second MOS transistor (31) operating as a transfer gate, and a second floating gate transistor (32) operating as a dummy cell. The second load (28) has the same characteristics as the first load (24). The second load (28) is composed of first and second load elements (28A, 28B). The second floating gate transistor (32) is constantly supplied with power voltage. When a shift in the thre shold voltage of the first floating gate transistor (22) is monitored, the first load element (28A) of the second load (28) is disconnected from the input terminal of the differential amplifier (26), and only the second load element (28B) remains connected to the input terminal. The gate of the second MOS transistor (31) is supplied with the high potential. A gradually increasing potential is applied to the gates of the first MOS transistor (23) and the first floating gate transistor (22). The potential is detected when the data of the first floating gate transistor changes from "0" to "1".