The sense amp circuit includes a first node given a first, positive constant voltage larger than a fixed potential before reading, a second node given a second, negative constant voltage smaller than the fixed potential before reading, and a third node to be connected to the first and second nodes on reading. A first transistor is connected between the first node and the bit line and operative to turn on when the potential on the bit line becomes smaller than the fixed potential. A second transistor is connected between the second node and the bit line and operative to turn on when the potential on the bit line becomes larger than the fixed potential. A first capacitor is connected between the first node and the fixed potential. A second capacitor is connected between the second node and the fixed potential.