1. An amplifier including a differential output stage and a differential input stage, wherein
the differential output stage includes a first current path and a second current path outputting differential signals and connected between a first power supply and a second power supply,
the first current path includes a first resistance element between the first power supply and a first node, a first transistor and a second transistor between the first node and a second node, and a second resistance element between the second node and the second power supply,
the second current path includes a third resistance element between the first power supply and a third node, a third transistor and a fourth transistor between the third node and a fourth node, and a fourth resistance element between the fourth node and the second power supply,
a gate of the first transistor is connected to the fourth node,
a gate of the second transistor is connected to the third node,
a gate of the third transistor is connected to the second node,
a gate of the fourth transistor is connected to the first node, and
current output from the differential input stage is connected to the first node and the third node.
2. The amplifier according to claim 1, wherein the first resistance element to the fourth resistance element are formed by transistors.
3. The amplifier according to claim 1, wherein the differential input stage behaves at around first power supply voltage.
4. An amplifier including a differential output stage, a first differential input stage, and a second differential input stage, wherein
the differential output stage includes a first current path and a second current path outputting differential signals and connected between a first power supply and a second power supply,
the first current path includes a first resistance element between the first power supply and a first node, a first transistor and a second transistor between the first node and a second node, and a second resistance element between the second node and the second power supply,
the second current path includes a third resistance element between the first power supply and a third node, a third transistor and a fourth transistor between the third node and a fourth node, and a fourth resistance element between the fourth node and the second power supply,
a gate of the first transistor is connected to the fourth node,
a gate of the second transistor is connected to the third node,
a gate of the third transistor is connected to the second node,
a gate of the fourth transistor is connected to the first node,
current output from the first differential input stage is connected to the first node and the third node, and
current output from the second differential input stage is connected to the second node and the fourth node.
5. The amplifier according to claim 4, wherein the first resistance element to the fourth resistance element are formed by transistors.
6. The amplifier according to claim 4, wherein the first differential input stage is turned off when differential input signal is around first power supply voltage, and the second differential input stage is turned off when differential input signal is around second power supply voltage.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method of making a porous three-dimensional fiber structure comprising a coherent three-dimensional substrate of refractory fibers, wherein carbon nanotubes are incorporated in the fiber structure by being grown on the refractory fibers of the substrate, after impregnation by a composition comprising at least one catalyst for carbon nanotube growth, so as to obtain a three-dimensional structure made of refractory fibers and enriched in carbon nanotubes.
2. A method according to claim 1, comprising the successive steps of:
impregnating two-dimensional plies of refractory fibers with a composition containing at least one catalyst for carbon nanotube growth;
forming a three-dimensional substrate by superposing and bonding together a plurality of impregnated two-dimensional plies; and
causing carbon nanotubes to grow within the three-dimensional substrate.
3. A method according to claim 2, wherein the two-dimensional plies are bonded together by needling.
4. A method according to claim 1, comprising the successive steps of:
a) impregnating refractory fiber two-dimensional plies with a composition containing at least one catalyst for carbon nanotube growth;
b) causing carbon nanotubes to grow within the two-dimensional plies; and
c) forming the three-dimensional fiber structure by superposing and bonding together two-dimensional plies of refractory fibers in which at least some of the plies contain carbon nanotubes obtained by steps a) and b).
5. A method according to claim 4, wherein the three-dimensional fiber structure is formed by stacking two-dimensional plies having varying quantities of carbon nanotubes.
6. A method according to claim 4, wherein the two-dimensional are bonded together by needling.
7. A method according to claim 6, wherein a layer of free fibers is deposited on each of at least some of the two-dimensional plies, prior to needling.
8. A method according to claim 6, wherein the two-dimensional plies with carbon nanotubes are moistened prior to needling.
9. A method according to claim 1, comprising the successive steps of:
making a three-dimensional substrate of refractory fibers;
impregnating the substrate with a composition containing at least one catalyst for carbon nanotube growth; and
causing carbon nanotubes to grow within the three-dimensional substrate.
10. A method according to claim 9, wherein making the three-dimensional substrate includes superposing and bonding together two-dimensional plies.
11. A method according to claim 10, wherein the three-dimensional plies are bonded together by needling.
12. A method according to claim 9, wherein the three-dimensional substrate of refractory fibers is made by three-dimensional weaving, knitting, or braiding.
13. A method according to claim 2, wherein impregnation is performed using a composition containing at least one catalyst for carbon nanotube growth on refractory fibers having a specific surface area of not less than 10 m2\xb7g.
14. A method according to claim 2, wherein surface treatment is performed on the refractory fibers in order to impart a specific surface area thereon of not less than 10 m2\xb7g.
15. A method according to claim 14, wherein surface treatment is performed by controlled oxidation.
16. A method according to claim 14, wherein surface treatment is performed by acid attack.
17. A method according to claim 14, wherein the surface treatment of the refractory fibers is performed prior to impregnation with a composition containing at least one catalyst for carbon nanotube growth.
18. A method according to claim 14, wherein the surface treatment of the refractory fibers is performed after impregnation with a composition containing at least one catalyst for carbon nanotube growth.
19. A method according to claim 2, wherein impregnation is performed with a composition containing a solution of at least one salt of a metal constituting a catalyst for carbon nanotube growth.
20. A method according to claim 19, further including a step of eliminating particles of metal catalyst after the carbon nanotube enriched three-dimensional structure has been made.
21. A method according to claim 1, wherein additional carbon nanotubes are introduced into the pores of at least one surface portion of the fiber structure.
22. A method according to claim 21, wherein additional carbon nanotubes are introduced by bringing a suspension of carbon nanotubes in a liquid to the surface of the fiber structure.
23. A coherent three-dimensional structure comprising a three-dimensional porous substrate of refractory fibers, and carbon nanotubes which are distributed throughout the pores of the substrate.
24. A structure according to claim 23, wherein the refractory fibers are made of carbon.
25. A structure according to claim 23, wherein the refractory fibers are made of ceramic.
26. A structure according to claim 23, wherein the carbon nanotubes constitute, by weight, 5% to 200% of the weight of the refractory fiber substrate.
27. A structure according to claim 23, wherein the three-dimensional substrate is made of up two-dimensional plies bonded together by needling.
28. A thermostructural composite material part comprising a fiber reinforcement in the form of a three-dimensional fiber structure and a refractory matrix, wherein the three-dimensional fiber structure comprises a three-dimensional porous substrate of refractory fibers and carbon nanotubes which are distributed throughout the pores of the substrate.
29. A composite material part according to claim 28, wherein the refractory fibers are made of carbon.
30. A composite material part according to claim 28, wherein the refractory fibers are made of ceramic.
31. A composite material part according to claim 28, wherein the carbon nanotubes constitute, by weight, 5% to 200% of the weight of the refractory fiber substrate.
32. A composite material part according to claim 28, wherein the three-dimensional substrate is made up of two-dimensional plies bonded together by needling.
33. A composite material part according to claim 28, wherein the carbon nanotubes are randomly oriented.
34. A composite material part according to claim 28, wherein the carbon nanotubes are distributed throughout said pores in substantially uniform manner.
35. A composite material part according to claim 28, wherein the carbon nanotubes adhere to the fibers of the fiber substrate.
36. A composite material part according to claim 28, wherein the carbon nanotubes are separated from the fibers of the fiber substrate.
37. A composite material part according to claim 28, wherein the fiber structure has a greater density of nanotubes in pores of the substrate located in the vicinity of a surface of the fiber structure than in other pores.
38. A friction part made of a thermostructural composite material having a carbon fiber reinforcement densified with a matrix, wherein said reinforcement comprises:
a three-dimensional fibrous structure formed of a plurality of two-dimensional carbon fiber plies which are superposed and bonded together by needling, and
carbon nanotubes distributed throughout the matrix in spaces corresponding to original pores of the fibrous structure.
39. A friction par according to claim 38, wherein the carbon nanotubes constitute, by weight, 5% to 200% of the weight of the fibrous structure.
40. A friction par according to claim 38, wherein the carbon nanotubes are randomly oriented.
41. A friction par according to claim 38, wherein the carbon nanotubes are distributed throughout said pores in substantially uniform manner.
42. A friction par according to claim 38, wherein the carbon nanotubes adhere to the fibers of the fibrous structure.
43. A friction par according to claim 38, wherein the carbon nanotubes are separated from the fibers of the fibrous structure.