In the output operation, such switches as 5902, 106, 107, 103, and 105 may be arranged anywhere as long as the elements are connected as shown in FIG. 67 in which a gate potential of the switching transistor 102 and the current source transistor 101 is held in the capacitor 104, the switching transistor 102 performs the current source operation, and a current which flows through the switching tran