| 摘要 |
PURPOSE:To enable to render the line decoder to be selected in the word line containing faulty bits into an electrically non-selective state, in the case when the fuse within a line decoder breaks during its test in order that a reserve decoder is to be selected, the detection is performed to the effect that said reserve decoder has been selected. CONSTITUTION:Normally, a reserve coder 6 is not activated and the output 21 of a non-inverting amplifier 20 is at low voltage, and a MOST QN mounted in parallel with the MOSTs of normal decoders 4 is brought to a non-conductive state. Consequently, the word lines 13 selected by means of the normal decoders are selected by word line drive signals. When the defectiveness of a memory cell connected to some line is discovered through a test, the fuses F1-F6 are turned OFF so that the reserve line decoder is activated. When selecting lines, the output of the non-inverting amplifier 20 is at high voltage when the reserve decoder is activated, the MOST QN set up to the normal decoder is conducted, and the normal decoder is inactivated. Accordingly, the number of the fuses to be turned OFF can be reduced because the decoder is inactivated electrically in order to bring the word line with the defective bit to a nonselective state. |
