Abstract: A plurality of charge storage cells, each including first and second storage regions, are provided in a semiconductor substrate. Means are provided responsive to a scanning signal for introducing into each of the first charge storage regions a respective quantity of charge proportional to a respective sample of an analog signal. Means are provided responsive to the bits of one value of a digital reference word for maintaining storage of the analog samples in the first storage regions of the cells associated with such bits of one value. Means are provided responsive to bits of the other value of the digital reference word for transferring the analog samples to the second storage regions of the cells associated with such bits of the other value.