The present invention enables to ensure printing the entire desired image. A Digital Signal Processor includes a database of chemical signatures and corresponding chemicals. The supporting rods are curved to bulge outwardly to a first position. A plurality of gate electrodes face to the base region and the source region via a gate insulating film. A signal processing apparatus is provided which includes switches provided for a plurality of signal sources, a common line to which signals from the plurality of signal sources are sequentially transferred, and a parasitic capacitance control circuit for controlling parasitic capacitance of the common line in accordance with the level of the signal on the common line.