DC-DC converter and semiconductor device
View Patent ↗A DC-DC converter with low power consumption and high power conversion efficiency is provided. The DC-DC converter includes a first transistor and a control circuit. The control circuit includes an operational amplifier generating a signal that controls switching of the first transistor, a bias circuit generating a bias potential supplied to the operational amplifier, and a holding circuit holding the bias potential. The holding circuit includes a second transistor and a capacitor to which the bias potential is supplied. The first transistor and the second transistor include a first oxide semiconductor film and a second oxide semiconductor film, respectively. The first oxide semiconductor film and the second oxide semiconductor film each contain In, M (M is Ga, Y, Zr, La, Ce, or Nd), and Zn. The atomic ratio of In to M in the first oxide semiconductor film is higher than that in the second oxide semiconductor film.
1. A semiconductor device comprising:
an operational amplifier;
a first transistor; and
a second transistor over the first transistor with an insulating film interposed therebetween,
wherein an output terminal of the operational amplifier is electrically connected to a gate of the first transistor,
wherein a first terminal of the first transistor is electrically connected to an output terminal of the semiconductor device,
wherein a first terminal of the second transistor is electrically connected to the operational amplifier,
wherein the first transistor comprises a first oxide semiconductor film comprising a channel formation region, and
wherein the second transistor comprises a second oxide semiconductor film comprising a channel formation region.
2. The semiconductor device according to claim 1 ,
wherein the operational amplifier is configured to generate a control signal supplied to the gate of the first transistor,
wherein the first transistor is configured to supply a voltage from the output terminal of the semiconductor device, and
wherein the second transistor is configured to hold a bias potential supplied to the operational amplifier.
3. The semiconductor device according to claim 2 , further comprising a capacitor,
wherein the capacitor is configured to hold a charge corresponding to the bias potential.
4. The semiconductor device according to claim 1 , further comprising a coil between the first terminal of the first transistor and the output terminal of the semiconductor device.
5. The semiconductor device according to claim 4 , further comprising a diode between the first terminal of the first transistor and a second output terminal of the semiconductor device,
wherein a second terminal of the first transistor is electrically connected to a power source.
6. The semiconductor device according to claim 1 , further comprising a coil between the first terminal of the first transistor and a power source.
7. The semiconductor device according to claim 6 , further comprising a diode between the first terminal of the second transistor and the output terminal of the semiconductor device,
wherein a second terminal of the first transistor is electrically connected to a second output terminal of the semiconductor device.
8. A semiconductor device comprising:
an operational amplifier;
a first transistor; and
a second transistor over the first transistor with an insulating film interposed therebetween,
wherein an output terminal of the operational amplifier is electrically connected to a gate of the first transistor,
wherein a first terminal of the first transistor is electrically connected to an output terminal of the semiconductor device,
wherein a first terminal of the second transistor is electrically connected to the operational amplifier,
wherein the first transistor comprises a first oxide semiconductor film comprising a channel formation region and a pair of first gate electrodes between which the first semiconductor film is provided, and
wherein the second transistor comprises a second oxide semiconductor film comprising a channel formation region and a pair of second gate electrodes between which the second semiconductor film is provided.
9. The semiconductor device according to claim 8 ,
wherein the operational amplifier is configured to generate a control signal supplied to the gate of the first transistor,
wherein the first transistor is configured to supply a voltage from the output terminal of the semiconductor device, and
wherein the second transistor is configured to hold a bias potential supplied to the operational amplifier.
10. The semiconductor device according to claim 9 , further comprising a capacitor,
wherein the capacitor is configured to hold a charge corresponding to the bias potential.
11. The semiconductor device according to claim 8 , further comprising a coil between the first terminal of the first transistor and the output terminal of the semiconductor device.
12. The semiconductor device according to claim 11 , further comprising a diode between the first terminal of the first transistor and a second output terminal of the semiconductor device,
wherein a second terminal of the first transistor is electrically connected to a power source.
13. The semiconductor device according to claim 8 , further comprising a coil between the first terminal of the first transistor and a power source.
14. The semiconductor device according to claim 13 , further comprising a diode between the first terminal of the second transistor and the output terminal of the semiconductor device,
wherein a second terminal of the first transistor is electrically connected to a second output terminal of the semiconductor device.
15. A semiconductor device comprising:
an operational amplifier;
a first transistor; and
a second transistor over the first transistor with an insulating film interposed therebetween,
wherein an output terminal of the operational amplifier is electrically connected to a gate of the first transistor,
wherein a first terminal of the first transistor is electrically connected to an output terminal of the semiconductor device,
wherein a first terminal of the second transistor is electrically connected to the operational amplifier,
wherein the first transistor comprises a first oxide semiconductor film comprising a channel formation region,
wherein the second transistor comprises a second oxide semiconductor film comprising a channel formation region,
wherein the first oxide semiconductor film comprises at least one of In and Zn,
wherein the second oxide semiconductor film comprises In, M, and Zn, and
wherein M is at least one of Ga, Y, Zr, La, Ce, and Nd.
16. The semiconductor device according to claim 15 ,
wherein the operational amplifier is configured to generate a control signal supplied to the gate of the first transistor,
wherein the first transistor is configured to supply a voltage from the output terminal of the semiconductor device, and
wherein the second transistor is configured to hold a bias potential supplied to the operational amplifier.
17. The semiconductor device according to claim 16 , further comprising a capacitor,
wherein the capacitor is configured to hold a charge corresponding to the bias potential.
18. The semiconductor device according to claim 15 , further comprising a coil between the first terminal of the first transistor and the output terminal of the semiconductor device and a diode between the first terminal of the first transistor and a second output terminal of the semiconductor device,
wherein a second terminal of the first transistor is electrically connected to a power source.
19. The semiconductor device according to claim 15 , further comprising a coil between the first terminal of the first transistor and a power source and a diode between the first terminal of the second transistor and the output terminal of the semiconductor device,
wherein a second terminal of the first transistor is electrically connected to a second output terminal of the semiconductor device.