To provide a memory device which operates with low power consumption, has high reliability of the stored data, and is small-size, light-weight and inexpensive, and a driving method thereof. In speech recognition, optimal equalization factors for feature vectors of a plurality of speech frames corresponding to each probability density function in a speech model are determined based on the plurality of speech frames of the input speech and the speech model. A computer program for implementing the method, a receiver arrangement adapted to perform such investigation, and a communication apparatus using such receiver arrangement are also disclosed. A photosensitive chip is mounted in the chip receiving cavity, wherein at least partially a non-active surface of the chip is attached to the encapsulant filling the recessed region and is not in contact with the recessed region.