US Patent 7529133 Nonvolatile semiconductor storage apparatus and readout method

A semiconductor storage apparatus includes a plurality of data cells arranged in rows and columns. The data cells have MOS transistors having different types of operating characteristics to store data according to the types of the MOS transistors. Bit lines extend to the respective columns of data cells. The stored data is read out according to a cell current arising in the bit lines. One among the bit liens is taken as a reference bit line, and the bit line cell currents in the remaining bit lines are adjusted according to the value of the cell current arising in the reference bit line.