Semiconductor device

A semiconductor device comprising: a first transistor; a capacitor; a first switch; a second switch; a third switch; a fourth switch; and a current source supplying a current to the first transistor and the capacitor, wherein one of a source and a drain of the first transistor is electrically connected to one terminal of the first switch, wherein the other terminal of the first switch is electrically connected to a gate of the first transistor and one terminal of the capacitor, wherein the other terminal of the capacitor is electrically connected to one terminal of the second switch and one terminal of the third switch, and wherein the other terminal of the third switch is electrically connected to the other of the source and the drain of the first transistor and one terminal of the fourth switch.