As shown in FIG. 46A, the transistors 461, 464, and 468 may be transistors with back gates. In each of the transistors 461 and 464 in FIG. 46A, the gate is electrically connected to the back gate. Thus, the gate and the back gate always have the same potential. The back gate of the transistor 468 is electrically connected to the node 467. Therefore, the back gate always has the same potential as the node 467.
As at least one of the transistors 461, 468, and 464, the transistor 100 or 200 described above can be used.
[Example of Pixel Circuit for Liquid Crystal Display Device]
The pixel circuit 534 in FIG. 45C includes the transistor 461 and the capacitor 463. The pixel circuit 534 in FIG. 45C is electrically connected to a liquid crystal element 462 that can function as a display element. It is preferable to use an OS transistor as the transistor 461.
