. "FIG. 4A is a graph for showing 2-bit digital data of two inputs (v(a),v(b)) depending on time; FIG. 4B shows an example of a voltage level in the ramp switch control signals vsw0, vsw1, vsw2, vsw3, and vsw4; FIG. 4C is a graph for showing the ramp signal vrampout, in which the analog data vdata converted by the DAC/ramp circuit and the fabrication process thereof become one ouput; and FIG. 4D is a" . . .