PURPOSE: To provide a reading circuit capable of expanding the reading room of a memory and reducing patterns and a peak current and a semiconductor storage device capable of operating a reading system using this circuit.
CONSTITUTION: A voltage variable circuit 9 for supplying a plurality of different sized potentials to word lines W1, W2,... is added to the semiconductor storage device for writing data of over 4 values in a memory cell 1. Then, by changing the size of a voltage impressed to the word line using this circuit, the data is read out. The reading operation is carried out being divided into plural times so as to read out the specified memory cell everytime the size of the voltage is changed. As the voltage used for the voltage variable circuit is the one equal to the threshold valve of the memory cell, the memory cell may be used, a power voltage is decreased and supplied.
KATO HIDEO
MOCHIZUKI YOSHIO
