Semiconductor device and operation method thereof
A semiconductor device capable of obtaining the threshold voltage of a transistor is provided. The semiconductor device includes a first transistor, a first capacitor, a first output terminal, a first switch, and a second switch. A gate and a source of the first transistor are electrically connected to each other. A first terminal of the first capacitor is electrically connected to the source. A second terminal and the first output terminal of the first capacitor are electrically connected to a back gate of the first transistor. The first switch controls input of a first voltage to the back gate. A second voltage is input to a drain of the first transistor. The second switch controls input of a third voltage to the source.
1. A semiconductor device comprising a first transistor, a first capacitor, a first output terminal, a first switch, and a second switch,
wherein a gate and a source of the first transistor are electrically connected to each other,
wherein a first terminal of the first capacitor and the first output terminal are electrically connected to a back gate of the first transistor,
wherein a second terminal of the first capacitor is electrically connected to the source,
wherein the first switch controls input of a first voltage to the back gate,
wherein a second voltage is input to a drain of the first transistor, and
wherein the second switch controls input of a third voltage to the source.
2. The semiconductor device according to claim 1 ,
wherein the first switch and the second switch are each a transistor including a metal oxide in a channel formation region.
3. The semiconductor device according to claim 1 ,
wherein the first transistor is an n-channel transistor,
wherein the first to third voltages are constant voltages, and
wherein the second voltage and the third voltage are set so that the first transistor shows normally-on characteristics and a voltage between the drain and the source is higher than 0 V.
4. The semiconductor device according to claim 1 ,
wherein the first transistor is a p-channel transistor,
wherein the first to third voltages are constant voltages, and
wherein the second voltage and the third voltage are set so that the first transistor shows normally-on characteristics and a voltage between the drain and the source is lower than 0 V.
5. The semiconductor device according to claim 1 , further comprising a second transistor comprising a back gate,
wherein a voltage input to the back gate of the second transistor is changed in accordance with a fourth voltage output from the first output terminal.
6. The semiconductor device according to claim 1 , further comprising a third transistor,
wherein a voltage input to a gate of the third transistor is changed in accordance with a fourth voltage output from the first output terminal.
7. The semiconductor device according to claim 1 , further comprising a second capacitor, a current-voltage converter circuit, and an amplifier circuit,
wherein a first terminal of the second capacitor is electrically connected to the first output terminal,
wherein a second terminal of the second capacitor is electrically connected to an input terminal of the current-voltage converter circuit, and
wherein the amplifier circuit amplifies a fifth voltage output from the current-voltage converter circuit and outputs a sixth voltage.
8. The semiconductor device according to claim 7 ,
wherein the current-voltage converter circuit is a source follower circuit.
9. The semiconductor device according to claim 7 ,
wherein the sixth voltage decreases as temperature rises.
10. The semiconductor device according to claim 7 ,
wherein the amplifier circuit is an operational amplifier.
11. The semiconductor device according to claim 7 , further comprising a fourth transistor comprising a back gate,
wherein a voltage input to the back gate of the fourth transistor is changed in accordance with the sixth voltage.
12. The semiconductor device according to claim 7 , further comprising a fifth transistor,
wherein a voltage input to a gate of the fifth transistor is changed in accordance with the sixth voltage.
13. A method for operating the semiconductor device according to claim 1 , comprising:
turning on the first switch and the second switch;
turning on the first switch and turning off the second switch;
turning off the first switch and turning off the second switch; and
turning off the first switch and turning on the second switch.
14. A semiconductor device comprising a first transistor, a first capacitor, a first output terminal, a first switch, a second switch, a second capacitor, a current-voltage converter circuit, and an amplifier circuit,
wherein a gate and a source of the first transistor are electrically connected to each other,
wherein a first terminal of the first capacitor and the first output terminal are electrically connected to a back gate of the first transistor,
wherein a second terminal of the first capacitor is electrically connected to the source,
wherein the first switch controls input of a first voltage to the back gate,
wherein a second voltage is input to a drain of the first transistor,
wherein the second switch controls input of a third voltage to the source,
wherein the first switch and the second switch are each a transistor including a metal oxide in a channel formation region,
wherein a first terminal of the second capacitor is electrically connected to the first output terminal,
wherein a second terminal of the second capacitor is electrically connected to an input terminal of the current-voltage converter circuit, and
wherein the amplifier circuit amplifies a fifth voltage output from the current-voltage converter circuit and outputs a sixth voltage.
15. The semiconductor device according to claim 14 ,
wherein the current-voltage converter circuit is a source follower circuit.
16. The semiconductor device according to claim 14 ,
wherein the sixth voltage decreases as temperature rises.
17. A method for operating the semiconductor device according to claim 14 , comprising:
turning on the first switch and the second switch;
turning on the first switch and turning off the second switch;
turning off the first switch and turning off the second switch; and
turning off the first switch and turning on the second switch.