Semiconductor device, semiconductor wafer, and electronic device

A semiconductor device comprising:

• a first transistor and a second transistor each comprising a gate, a back gate, and a metal oxide in a channel formation region;
• and
• an operational amplifier,
• wherein an inverting input terminal of the operational amplifier is electrically connected to a first terminal of the first transistor and the gate of the first transistor,
• wherein a second terminal of the first transistor is electrically connected to a first terminal of the second transistor,
• wherein the gate of the second transistor is electrically connected to the inverting input terminal of the operational amplifier,
• wherein an output terminal of the operational amplifier is electrically connected to a second terminal of the second transistor,
• wherein the operational amplifier is a single-polarity circuit using transistors comprising the metal oxide in channel formation regions, and
• wherein an off-state current of the first transistor and an off-state current of the second transistor are made less than or equal to 1.0×10−15 A by inputting a potential that shifts a threshold voltage of the first transistor and a threshold voltage of the second transistor to a positive side, to the back gate of the first transistor and the back gate of the second transistor.