DRAM sense amplifier having pre-charged transistor body nodes

• US 6,466,499 B1
• Filed: 07/11/2000
• Issued: 10/15/2002
• Est. Priority Date: 07/11/2000
• Status: Expired due to Term

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Blodgett, Greg A.
• Primary Examiner(s): Dinh, Son T.
• Application Number:
  US09/614,119
• Time in Patent Office: 826 Days
• Field of Search: 365/207, 365/189.01, 365/230.01, 365/185.21, 365/205, 365/206, 365/208
• US Class Current: 365/207
• CPC Class Codes: G11C 11/4074 Power supply or voltage generation circuits, e.g. bias voltage generators, substrate voltage generators, back-up power, power control circuits
• CPC Class Codes: G11C 11/4091 Sense or sense/refresh amplifiers, or associated sense circuitry, e.g. for coupled bit-line precharging, equalising or isolating
• CPC Class Codes: G11C 7/065 Differential amplifiers of latching type

Abstract

A DRAM sense amplifier that reduces the leakage current through the sense amplifier circuitry while the array is active, while controlling the body voltage of the sense amplifier transistors to improve performance of the sense amplifier circuitry is disclosed. The body nodes of the sense amplifier transistors are pre-charged to a voltage potential, such as for example Vcc/2. The body nodes are disconnected from the pre-charge voltage while the sense amplifier is enabled, i.e., during an access operation, but the threshold voltage V_t of the sense amplifier transistors will be lower during sensing due to the pre-charge level. As the body potential drops during sensing, the threshold voltage V_t will increase, thereby reducing the leakage current that flows through the sense amplifier while the digit lines are separated.

Claims

1. A sense amplifier comprising:

a first amplifier circuit adapted to be connected between a pair of digit lines of a memory device, said first amplifier circuit having a first transistor and a second transistor, each of said first transistor and said second transistor having a body node;

a third transistor having a first terminal connected to said body node of said first and second transistor, a second terminal connected to a voltage potential, and a gate terminal connected to receive a first control signal,

wherein before said sense amplifier is activated, said first control signal turns on said third transistor to connect said voltage potential to said body node of said first and second transistor to thereby charge said body node of said first and second transistor to said voltage potential, and when said sense amplifier is activated said first control signal turns off said third transistor to disconnect said voltage potential from said body node of said first and second transistor.

2. The sense amplifier according to claim 1, wherein said first amplifier circuit is an N-sense amplifier.

3. The sense amplifier according to claim 2, wherein said first and second transistors are cross-coupled NMOS transistors.

4. The sense amplifier according to claim 1, wherein said first amplifier circuit is a P-sense amplifier.

5. The sense amplifier according to claim 4, wherein said first and second transistors are cross-coupled PMOS transistors.

6. The sense amplifier according to claim 1, wherein said voltage potential is Vcc/2.

7. The sense amplifier according to claim 1, wherein said first control signal is an equilibration signal.

8. The sense amplifier according to claim 1, wherein said first terminal of said third transistor is connected to said body node of said first and second transistor by a metal strap routed through said sense amplifier.

9. The sense amplifier according to claim 1, further comprising:

a second amplifier circuit adapted to be connected between said pair of digit lines of said memory device, said second amplifier circuit having a first transistor and a second transistor, each of said first transistor and said second transistor of said second amplifier circuit having a body node,

wherein said body node of said first and second transistor of said second amplifier circuit are adapted to be coupled to said voltage potential.

10. The sense amplifier according to claim 9, wherein said body node of said first and second transistor of said second amplifier circuit are connected to said first terminal of said third transistor, and wherein when said first control signal turns on said third transistor said body node of said first and second transistor of said second amplifier circuit are coupled to said voltage potential to thereby charge said body node of said first and second transistor of said second amplifier circuit to said voltage potential, and when said first control signal turns off said third transistor said voltage potential is disconnected from said body node of said first and second transistor of said second amplifier circuit.

11. The sense amplifier according to claim 9, further comprising:

a fourth transistor having a first terminal connected to said body node of said first and second transistor of said second amplifier circuit, a second terminal connected to said voltage potential, and a gate terminal connected to receive a second control signal,

wherein before said sense amplifier is activated, said second control signal turns on said fourth transistor to couple said voltage potential to said body node of said first and second transistor of said second amplifier circuit to thereby charge said body node of said first and second transistor of said second amplifier circuit to said voltage potential, and when said sense amplifier is activated said second control signal turns off said fourth transistor to disconnect said voltage potential from body node of said first and second transistor of said second amplifier circuit.

12. The sense amplifier according to claim 11, wherein said second control signal is an equilibration signal.

13. The sense amplifier according to claim 11, wherein said first control signal and said second control signal are identical signals.

14. The sense amplifier according to claim 11, wherein said first amplifier circuit is an N-sense amplifier and said second amplifier circuit is a P-sense amplifier.

15. The sense amplifier according to claim 14, wherein said first and second transistor of said first amplifier circuit are cross-coupled NMOS transistors and said first and second transistors of said second amplifier circuit are cross-coupled PMOS transistors.

16. The sense amplifier according to claim 11, wherein said voltage potential is Vcc/2.

17. The sense amplifier according to claim 1, wherein said first amplifier circuit further comprises:

a first diode connected between said body node of said first transistor and one of a source region and a drain region of said first transistor.

18. The sense amplifier according to claim 17, wherein said first amplifier circuit further comprises:

a second diode connected between said body node of said second transistor and one of a source region and a drain region of said second transistor.

19. A sense amplifier for a memory device comprising:

a first amplifier circuit connected between a pair of digit lines of said memory device, said first amplifier circuit including a plurality of transistors, each of said plurality of transistors having a body node;

a first control transistor having a first terminal connected to said body node of at least one of said plurality of transistors, a second terminal connected to a voltage potential, and a gate connected to a first control signal,

wherein before said sense amplifier is activated, said first control signal turns on said first control transistor to connect said voltage potential to said body node of said at least one of said plurality of transistors to thereby charge said body node of said at least one of said plurality of transistors to said voltage potential, and when said sense amplifier is activated said first control signal turns off said first control transistor to disconnect said voltage potential from said body node of said at least one of said plurality of transistors.

20. The sense amplifier according to claim 19, wherein said voltage potential is Vcc/2.

21. The sense amplifier according to claim 19, wherein said first control signal is an equilibration signal.

22. The sense amplifier according to claim 19, wherein said first amplifier circuit is an N-sense amplifier including a pair of cross-coupled NMOS transistors.

23. The sense amplifier according to claim 19, wherein said first amplifier circuit is a P-sense amplifier circuit including a pair of cross-coupled PMOS transistors.

24. The sense amplifier according to claim 19, further comprising:

a second amplifier circuit connected between a pair of digit lines of said memory device, said second amplifier circuit including a plurality of transistors, each of said plurality of transistors of said second amplifier circuit having a body node, said body node of at least one of said plurality of transistors being connected to said first terminal of said first control transistor;

wherein when said first control signal turns on said first control transistor, said body node of said at least one of said plurality of transistors of said second amplifier circuit is connected to said voltage potential to thereby charge said body node of said at least one of said plurality of transistors of said second amplifier circuit to said voltage potential, and when said first control signal turns off said first control transistor, said body node of said at least one of said plurality of transistors of said second amplifier circuit is disconnected from said voltage potential.

25. The sense amplifier according to claim 19, further comprising:

a second amplifier circuit connected between a pair of digit lines of said memory device, said second amplifier circuit including a plurality of transistors, each of said plurality of transistors of said second amplifier circuit having a body;

a second control transistor having a first terminal connected to said body node of at least one of said plurality of transistors of said second amplifier circuit, a second terminal connected to a voltage potential, and a gate connected to a second control signal,

wherein before said sense amplifier is activated, said second control signal turns on said second control transistor to connect said voltage potential to said body node of said at least one of said plurality of transistors of said second amplifier circuit to thereby charge said body node of said at least one of said plurality of transistors of said second amplifier circuit to said voltage potential, and when said sense amplifier is activated said second control signal turns off said second control transistor to disconnect said voltage potential from said body node of said at least one of said plurality of transistors of said second amplifier circuit.

26. The sense amplifier according to claim 25, wherein said first control signal and said second control signal are identical signals.

27. The sense amplifier according to claim 19, further comprising:

a plurality of diodes, each of said plurality of diodes being connected between a body node of a respective one of said plurality of transistors and one of a source and drain region of said respective one of said plurality of transistors.

28. A sense amplifier comprising:

an amplifier circuit formed in a substrate, said amplifier circuit comprising;

a first transistor having a body node of a first conductivity in said substrate;

a second transistor having a body node of said first conductivity in said substrate; and

active region in said substrate, said active region contacting said body nodes of said first and second transistors.

29. The sense amplifier according to claim 28, wherein said first conductivity is n-type and said active region is a p+ area.

30. The sense amplifier according to claim 28, wherein said amplifier circuit is an N-sense amplifier.

31. The sense amplifier according to claim 28, wherein said amplifier circuit is a P-sense amplifier.

32. A sense amplifier comprising:

an amplifier circuit formed in a substrate, said amplifier circuit comprising;

a first transistor having a body node of a first conductivity in said substrate;

a second transistor having a body node of said first conductivity in said substrate;

an active region in said substrate, said active region contacting said body nodes of said first and second transistors; and

a first diode connected between said body node of said first transistor and one of a source region and a drain region of said first transistor.

33. The sense amplifier according to claim 32, wherein said amplifier circuit further comprises:

a second diode connected between said body node of said second transistor and one of a source region and a drain region of said second transistor.

34. A memory device comprising:

a plurality of memory cells arranged in rows and columns;

a plurality of pairs of digit lines, each of said plurality of pairs of digit lines being associated with at least one of said plurality of memory cells; and

a plurality of sense amplifiers, each of said plurality of sense amplifiers comprising;

a first amplifier circuit connected between one of said plurality of pairs of digit lines, said first amplifier circuit having a first transistor and a second transistor, each of said first transistor and said second transistor having a body node;

a third transistor having a first terminal connected to said body node of said first and second transistor, a second terminal connected to a voltage potential, and a gate terminal connected to receive a first control signal,

wherein before said first amplifier circuit is activated, said first control signal turns on said third transistor to connect said voltage potential to said body node of said first and second transistor to thereby charge said body node of said first and second transistor to said voltage potential, and when said first amplifier circuit is activated said first control signal turns off said third transistor to disconnect said voltage potential from said body node of said first and second transistor.

35. The memory device according to claim 34, wherein said first amplifier circuit is an N-sense amplifier.

36. The memory device according to claim 35, wherein said first and second transistors are cross-coupled NMOS transistors.

37. The memory device according to claim 34, wherein said first amplifier circuit is a P-sense amplifier.

38. The memory device according to claim 37, wherein said first and second transistors are cross-coupled PMOS transistors.

39. The memory device according to claim 34, wherein said voltage potential is Vcc/2.

40. The memory device according to claim 34, wherein said first control signal is an equilibration signal.

41. The memory device according to claim 34, further comprising:

a second amplifier circuit connected between said one of said plurality of pairs of digit lines, said second amplifier circuit having a first transistor and a second transistor, each of said first transistor and said second transistor of said second amplifier circuit having a body node,

wherein said body node of said first and second transistor of said second amplifier circuit are adapted to be coupled to said voltage potential.

42. The memory device according to claim 41, wherein said body node of said first and second transistor of said second amplifier circuit are connected to said first terminal of said third transistor, and wherein when said first control signal turns on said third transistor said body node of said first and second transistor of said second amplifier circuit are coupled to said voltage potential to thereby charge said body node of said first and second transistor of said second amplifier circuit to said voltage potential, and when said first control signal turns off said third transistor said voltage potential is disconnected from said body node of said first and second transistor of said second amplifier circuit.

43. The memory device according to claim 41, further comprising:

a fourth transistor having a first terminal connected to said body node of said first and second transistor of said second amplifier circuit, a second terminal connected to said voltage potential, and a gate terminal connected to receive a second control signal,

wherein before said sense amplifier is activated, said second control signal turns on said fourth transistor to couple said voltage potential to said body node of said first and second transistor of said second amplifier circuit to thereby charge said body node of said first and second transistor of said second amplifier circuit to said voltage potential, and when said sense amplifier is activated said second control signal turns off said fourth transistor to disconnect said voltage potential from body node of said first and second transistor of said second amplifier circuit.

44. The memory device according to claim 43, wherein said second control signal is an equilibration signal.

45. The memory device according to claim 43, wherein said first control signal and said second control signal are identical signals.

46. The memory device according to claim 41, wherein said first amplifier circuit is an N-sense amplifier and said second amplifier circuit is a P-sense amplifier.

47. The memory device according to claim 46, wherein said first and second transistor of said first amplifier circuit are cross-coupled NMOS transistors and said first and second transistors of said second amplifier circuit are cross-coupled PMOS transistors.

48. The memory device according to claim 34, wherein said voltage potential is Vcc/2.

49. The memory device according to claim 34, wherein said first amplifier circuit further comprises:

a first diode connected between said body node of said first transistor and one of a source region and a drain region of said first transistor.

50. The memory device according to claim 49, wherein said first amplifier circuit further comprises:

a second diode connected between said body node of said second transistor and one of a source region and a drain region of said second transistor.

51. A memory device formed on a substrate, said memory device comprising:

a plurality of memory cells arranged in rows and columns;

a plurality of pairs of digit lines, each of said plurality of pairs of digit lines being associated with at least one of said plurality of memory cells; and

a plurality of sense amplifiers, each of said plurality of sense amplifiers comprising;

an amplifier circuit formed in said substrate, said amplifier circuit comprising;

a first transistor having a body node of a first conductivity in said substrate;

a second transistor having a body node of said first conductivity in said substrate; and

an active region in said substrate, said active region contacting said body nodes of said first and second transistors.

52. The memory device according to claim 51, wherein said first conductivity is n-type and said active region is a p+ area.

53. The memory device according to claim 51, wherein said amplifier circuit is an N-sense amplifier.

54. The memory device according to claim 51, wherein said amplifier circuit is a P-sense amplifier.

55. A memory device formed on a substrate, said memory device comprising:

a plurality of memory cells arranged in rows and columns;

a plurality of pairs of digit lines, each of said plurality of pairs of digit lines being associated with at least one of said plurality of memory cells; and

a plurality of sense amplifiers, each of said plurality of sense amplifiers comprising;

an amplifier circuit formed in said substrate, said amplifier circuit comprising;

a first transistor having a body node of a first conductivity in said substrate;

a second transistor having a body node of said first conductivity in said substrate;

an active region in said substrate, said active region contacting said body nodes of said first and second transistors; and

a first diode connected between said body node of said first transistor and one of a source region and a drain region of said first transistor.

56. The memory device according to claim 55, wherein said amplifier circuit further comprises:

a second diode connected between said body node of said second transistor and one of a source region and a drain region of said second transistor.

57. A processor system comprising:

a central processing unit; and

a memory device connected to said processing unit to receive data from and supply data to said central processing unit, said memory device comprising;

a plurality of memory cells arranged in rows and columns;

a plurality of pairs of digit lines, each of said plurality of pairs of digit lines being associated with at least one of said plurality of memory cells; and

a plurality of sense amplifiers, each of said plurality of sense amplifiers comprising;

a first amplifier circuit connected between one of said plurality of pairs of digit lines, said first amplifier circuit having a first transistor and a second transistor, each of said first transistor and said second transistor having a body node;

a third transistor having a first terminal connected to said body node of said first and second transistor, a second terminal connected to a voltage potential, and a gate terminal connected to receive a first control signal,

wherein before said first amplifier circuit is activated, said first control signal turns on said third transistor to connect said voltage potential to said body node of said first and second transistor to thereby charge said body node of said first and second transistor to said voltage potential, and when said first amplifier circuit is activated said first control signal turns off said third transistor to disconnect said voltage potential from said body node of said first and second transistor.

58. The processor system according to claim 57, wherein said first amplifier circuit is an N-sense amplifier.

59. The processor system according to claim 58, wherein said first and second transistors are cross-coupled NMOS transistors.

60. The processor system according t o claim 57, wherein said first amplifier circuit is a P-sense amplifier.

61. The processor system according to claim 60, wherein said first and second transistors are cross-coupled PMOS transistors.

62. The processor system according to claim 57, wherein said voltage potential is Vcc/2.

63. The processor system according to claim 57, wherein said first control signal is an equilibration signal.

64. The processor system according to claim 57, further comprising:

a second amplifier circuit connected between said one of said plurality of pairs of digit lines, said second amplifier circuit having a first transistor and a second transistor, each of said first transistor and said second transistor of said second amplifier circuit having a body node,

wherein said body node of said first and second transistor of said second amplifier circuit are adapted to be coupled to said voltage potential.

65. The processor system according to claim 64, wherein said body node of said first and second transistor of said second amplifier circuit are connected to said first terminal of said third transistor, and wherein when said first control signal turns on said third transistor said body node of said first and second transistor of said second amplifier circuit are coupled to said voltage potential to thereby charge said body node of said first and second transistor of said second amplifier circuit to said voltage potential, and when said first control signal turns off said third transistor said voltage potential is disconnected from said body node of said first and second transistor of said second amplifier circuit.

66. The processor system according to claim 64, further comprising:

a fourth transistor having a first terminal connected to said body node of said first and second transistor of said second amplifier circuit, a second terminal connected to said voltage potential, and a gate terminal connected to receive a second control signal,

wherein before said sense amplifier is activated, said second control signal turns on said fourth transistor to couple said voltage potential to said body node of said first and second transistor of said second amplifier circuit to thereby charge said body node of said first and second transistor of said second amplifier circuit to said voltage potential, and when said sense amplifier is activated said second control signal turns off said fourth transistor to disconnect said voltage potential from body node of said first and second transistor of said second amplifier circuit.

67. The processor system according to claim 66, wherein said second control signal is an equilibration signal.

68. The processor system according to claim 66, wherein said first control signal and said second control signal are identical signals.

69. The processor system according to claim 64, wherein said first amplifier circuit is an N-sense amplifier and said second amplifier circuit is a P-sense amplifier.

70. The processor system according to claim 69, wherein said first and second transistor of said first amplifier circuit are cross-coupled NMOS transistors and said first and second transistors of said second amplifier circuit are cross-coupled PMOS transistors.

71. The processor system according to claim 57, wherein said voltage potential is Vcc/2.

72. The processor system according to claim 57, wherein said central processing unit and said memory device are on a single chip.

73. The processor system according to claim 57, wherein said first amplifier circuit further comprises:

a first diode connected between said body node of said first transistor and one of a source region and a drain region of said first transistor.

74. The processor system according to claim 73, wherein said first amplifier circuit further comprises:

a second diode connected between said body node of said second transistor and one of a source region and a drain region of said second transistor.

75. A method for operating a sense amplifier, said sense amplifier including an amplifier circuit having a plurality of transistors, each of said plurality of transistors having a body node, said method comprising the steps of:

connecting said body node of at least one of said plurality of transistors of said amplifier circuit to a voltage potential;

charging said body node of said at least one of said plurality of transistors to said voltage potential;

disconnecting said body node of said at least one of said plurality of transistors of said amplifier circuit from said voltage potential; and

providing an operation signal to said amplifier circuit to activate said amplifier circuit.

76. The method according to claim 75, wherein said step of connecting further comprises:

turning on a control transistor to connect said body node of said at least one transistor of said amplifier circuit to said voltage potential.

77. The method according to claim 76, wherein said step of turning on further comprises:

providing a control signal to said transistor to turn on said transistor.

78. The method according to claim 77, wherein said control signal is an equilibration signal.

79. The method according to claim 78, wherein said step of disconnecting further comprises:

turning off said transistor to disconnect said body node of said at least one of said plurality of transistors of said amplifier circuit from said voltage potential.

80. The method according to claim 75, wherein said amplifier circuit is an N-sense amplifier.

81. The method according to claim 80, wherein said plurality of transistors includes a pair of cross-coupled NMOS transistors.

82. The method according to claim 75, wherein said amplifier circuit is a P-sense amplifier.

83. The method according to claim 82, wherein said plurality of transistors includes a pair of cross-coupled PMOS transistors.

84. The method according to claim 75, wherein said voltage potential is Vcc/2.

85. The method according to claim 75, further comprising:

decreasing said charge of said body node of said at least one of said plurality of transistors of said amplifier circuit.

86. The method according to claim 85, wherein said step of decreasing further comprises:

biasing a diode connected between said body node of said at least one of said plurality of transistors and one of a drain and source region of said at least one of said plurality of transistors, said biasing causing said diode to conduct, thereby decreasing said charge of said body node.

87. The method according to claim 85, wherein said step of decreasing further comprises:

increasing a threshold voltage of said at least one of said plurality of transistors of said amplifier circuit.

88. A method for operating a sense amplifier, said sense amplifier including a first and second amplifier circuit, each of said first and second amplifier circuits having a plurality of transistors, each of said plurality of transistors having a body node, said method comprising the steps of:

connecting said body node of at least one of said plurality of transistors of said first and second amplifier circuit to a voltage potential;

charging said body node of said at least one of said plurality of transistors of said first and second amplifier circuit to said voltage potential;

disconnecting said body node of said at least one of said plurality of transistors of said first and second amplifier circuit from said voltage potential; and

providing an operation signal to said amplifier circuit to activate said amplifier circuit.

89. The method according to claim 88, wherein said step of connecting further comprises:

turning on a control transistor to connect said body node of said at least one transistor of said first and second amplifier circuit to said voltage potential.

90. The method according to claim 89, wherein said step of turning one further comprises:

providing a control signal to said transistor to turn on said transistor.

91. The method according to claim 88, wherein said step of connecting further comprises:

turning on a first control transistor to connect said body node of said at least one transistor of said first amplifier circuit to said voltage potential; and

turning on a second control transistor to connect said body node of said at least one transistor of said second amplifier circuit to said voltage potential.

92. The method according to claim 91, wherein said steps of turning on further comprise:

providing a control signal to said first control transistor to turn on said first control transistor; and

providing said control signal to said second control transistor to turn on said second control transistor.

93. The method according to claim 92, wherein said control signal is an equilibration signal.

94. The method according to claim 91, wherein said step of turning on said first control transistor further comprises:

providing a first control signal to said first control transistor to turn on said first control transistor.

95. The method according to claim 94, wherein said step of turning on said second control transistor further comprises:

providing a second control signal to said second control transistor to turn on said second control transistor.

96. The method according to claim 88, wherein said first amplifier circuit is an N-sense amplifier.

97. The method according to claim 96, wherein said second amplifier circuit is an P-sense amplifier.

98. The method according to claim 88, wherein said voltage potential is Vcc/2.

99. The method according to claim 88, further comprising:

decreasing said charge of said body node of said at least one of said plurality of transistors of said first and second amplifier circuit.

100. The method according to claim 99, wherein said step of decreasing further comprises:

biasing a diode connected between said body node of said at least one of said plurality of transistors of said first and second amplifier circuit and one of a drain and source region of said at least one of said plurality of transistors, said biasing causing said diode to conduct, thereby decreasing said charge of said body node.

101. The method according to claim 99, wherein said step of decreasing further comprises:

increasing a threshold voltage of said at least one of said plurality of transistors of said first and second amplifier circuit.