A circuit for determining the value of a datum stored in an array memory cell of a non-volatile memory device having at least one reference memory cell of known content. The circuit has a determination stage, which compares an array electrical quantity, correlated to a current flowing in the array memory cell, with a reference electrical quantity, and supplies an output signal indicative of the datum, based on the comparison; and a generator circuit, provided with an input receiving a target electrical quantity correlated to a current flowing in use in the reference memory cell, and an output, which supplies the reference electrical quantity with a controlled value close or equal to that of the target electrical quantity. The generator circuit is provided with a variable generator, and a control unit connected to, and designed to control, the variable generator so that it will generate the controlled value of the reference electrical quantity.