TIME-MULTIPLEXED RESIDUE AMPLIFIER

• US 20110187573A1
• Filed: 02/01/2010
• Published: 08/04/2011
• Est. Priority Date: 02/01/2010
• Status: Active Grant

• Current Assignee: Analog Devices International Unlimited Company (Analog Devices, Inc.)
• Original Assignee: Linear Technology Corporation (Analog Devices, Inc.)
• Inventors: Thomas, Andrew J., Sousa, Joseph L.
• Granted Patent: US 8,018,370 B2
• Time in Patent Office: Days
• US Class Current: 341/155
• CPC Class Codes: H03F 2203/7215 the gated amplifier being switched on or off by a switch at the input of the amplifier
• CPC Class Codes: H03F 2203/7221 the gated amplifier being switched on or off by a switch at the output of the amplifier
• CPC Class Codes: H03F 3/211 using a combination of several amplifiers H03F3/60 takes precedence
• CPC Class Codes: H03F 3/72 Gated amplifiers, i.e. amplifiers which are rendered operative or inoperative by means of a control signal
• CPC Class Codes: H03M 1/0619 by dividing out the errors, i.e. using a ratiometric arrangement
• CPC Class Codes: H03M 1/1225 using time-division multiplexing
• CPC Class Codes: H03M 1/164 the steps being performed sequentially in series-connected stages H03M1/161 takes precedence
• CPC Class Codes: H03M 1/365 the voltage divider being a single resistor string
• CPC Class Codes: H03M 1/468 in which the input S/H circuit is merged with the feedback DAC array

Abstract

A system is configured and a method is provided for receiving an input ratio represented by a first input signal and a second input signal, and producing an output ratio represented by a first output signal and a second output signal. The system is constructed and the method is provided for alternately operating in at least two time periods, wherein in one time period the first input signal, a low accuracy amplifier, and the first output signal are selectively coupled, and in another time period the input signal, the low accuracy amplifier, a high accuracy attenuator, and the second output signal are selectively coupled so as to maintain the output ratio proportional to the input ratio.

Claims

1. A system including a circuit receiving an input ratio represented by a first input signal and a second input signal, and producing an output ratio represented by a first output signal and a second output signal, the circuit comprising:

a low accuracy amplifier and a high accuracy attenuator,

during one time period the first input signal and the low accuracy amplifier are selectively coupled to produce the first output signal and during another time period the second input signal, the low accuracy amplifier and the high accuracy attenuator are selectively coupled to produce the second output signal;

wherein the circuit maintains a highly accurate ratio between the output ratio and the input ratio.

2. The system according to claim 1, wherein the high accuracy attenuator is selectively coupled to the input of the low accuracy amplifier.

3. The system according to claim 1, wherein the high accuracy attenuator is selectively coupled to the output of the low accuracy amplifier.

4. The system according to claim 1, wherein the high accuracy attenuator comprises a first high accuracy attenuator circuit selectively coupled to the input of the low accuracy amplifier and a second high accuracy attenuator circuit selectively coupled to the output of the low accuracy amplifier circuit.

5. The system according to claim 1, wherein the first input signal is provided as the difference between input signals applied at least two distinct times.

6. The system according to claim 1, wherein the second input signal is provided as the difference between input signals applied at least two distinct times.

7. The system according to claim 1, further including storage circuitry operative to provide at substantially the same time output signals indicative of the first and second output signal of the circuit.

8. The system according to claim 7, wherein the storage circuitry produces output signals during a time period distinct from the time periods during which the first and second input signals are selectively coupled to the circuit.

9. The system according to claim 1, wherein the system operates to provide an analog-to-digital conversion function.

10. The system according to claim 9, wherein the system incorporates an analog-to-digital converter producing a digital output signal responsive to the output ratio of the circuit.

11. The system according to claim 10, wherein the analog-to-digital converter comprises a system constructed in accordance with claim 9.

12. The system according to claim 10, wherein the analog-to-digital converter incorporates a flash analog-to-digital converter.

13. The system according to claim 10, wherein the analog-to-digital converter operates in part by successive approximation.

14. The system according to claim 9, wherein the system incorporates an analog-to-digital-converter coupled to the input signals of the circuit.

15. The system according to claim 14, wherein the analog-to-digital converter incorporates a flash analog-to-digital converter.

16. The system according to claim 14, wherein the analog-to-digital converter operates in part by successive approximation.

17. An analog to digital conversion system including a multi-stage circuit comprising:

at least two stages each including a first signal path constructed to conduct at least a portion of an analog input signal, and a second signal path constructed to conduct at least a portion of an analog reference signal;

at least one amplifier having a gain, an input and an output; and

a time multiplexer constructed to operate alternately in at least two time periods, wherein

(a) during a first time period the first signal path of a first stage is connected to the input of the amplifier and the output of the amplifier is connected to the first signal path of a second stage, and

(b) during a second time period the second signal path of a first stage is connected to the input of the amplifier and the output of the amplifier is connected to the second signal path of the second stage,

so that the analog input signal and analog reference signal are each amplified by the same gain as each is respectively transmitted from the first to the second stages during the first and second time periods.

18. A system according to claim 17, further including a signal attenuator for attenuating the analog reference signal in the second signal path of at least one of the stages.

19. A system according to claim 18, wherein the attenuator is disposed in the second signal path of the first stage.

20. A system according to claim 18, wherein the attenuator is disposed in the second signal path of the second stage.

21. A system according to claim 17, further including at least two signal attenuators for respectively attenuating the analog reference signal in the second signal path of the first and second stages.

22. A system according to claim 17, further including a sample and hold circuit constructed and arranged to sample and hold one of the analog signals in the second stage during one of the time periods so that it can be compared to the other of the analog signals in the next subsequent time period.

23. A system according to claim 22, wherein the sample and hold circuit is disposed in one of the signal paths of the second stage.

24. A system according to claim 23, wherein the sample and hold circuit is disposed in the second signal path of the second stage.

25. A system according to claim 23, wherein the sample and hold circuit is disposed in the first signal path of the second stage.

26. A system according to claim 17, further including at least two sample and hold circuits respectively disposed in the first and second signal paths of the second stage.

27. A system according to claim 17, wherein the first stage operates in part as a flash analog-to-digital converter.

28. A system according to claim 17, wherein the first stage operates in part by successive approximation.

29. A system according to claim 17, wherein the second stage operates in part as a flash analog-to-digital converter.

30. A system according to claim 17, wherein the second stage operates in part by successive approximation.

31. A system according to claim 17, wherein the first or second stage operates in part as a system constructed in accordance with claim 17.

32. A multi-stage analog to digital converter for converting an analog input signal to a digital output signal, comprising:

a plurality of stages constructed and arranged so as to quantize the analog input signal by comparing the input signal in the first stage and a residue signal in each subsequent stage with a reference signal provided to each stage, and an interstage amplifier disposed between each set of interconnected stages and operative so as to apply the same amplifier gain to the residue and reference signals provided to the subsequent stage.

33. A multi-stage analog-to-digital converter according to claim 32, further including a time-multiplexer constructed and arranged to multiplex each interstage amplifier so as to amplify each residue and each reference signal provided to each subsequent stage

34. A multi-stage analog-to-digital converter according to claim 33, further including a signal attenuator constructed to attenuate the reference signal provided to each subsequent stage.

35. A multi-stage analog-to-digital converter according to claim 34, wherein the attenuator is constructed to attenuate the reference signal prior to being provided to the interstage amplifier.

36. A multi-stage analog-to-digital converter according to claim 34, wherein the attenuator is constructed to attenuate the reference signal subsequent to being provided to the interstage amplifier.

37. A multi-stage analog-to-digital converter according to claim 34, wherein the attenuator is constructed to attenuate the reference signal prior to and subsequent to being provided to the interstage amplifier.

38. A multi-stage analog-to-digital converter according to claim 33, wherein a sample and hold circuit is provided to sample and hold the residue signal in each subsequent stage.

39. A multi-stage analog-to-digital converter according to claim 33, wherein a sample and hold circuit is provided to sample and hold the reference signal of each subsequent stage.

40. A multi-stage analog-to-digital converter according to claim 33, wherein sample-and-hold circuits are provided to sample and hold the residue signal and reference signal of each subsequent stage.

41. A multi-stage analog-to-digital converter according to claim 32, wherein at least one of the plurality of stages operates as a flash analog-to-digital converter.

42. A multi-stage analog-to-digital converter according to claim 32, wherein at least one of the plurality of stages operates as a successive-approximation analog-to-digital converter.

43. A method of receiving an input ratio represented by a first input signal and a second input signal, and producing an output ratio represented by a first output signal and a second output signal, the method comprising:

alternately operating in at least two time periods, wherein in one time period the first input signal, a low accuracy amplifier, and the first output signal are selectively coupled, and in another time period the input signal, the low accuracy amplifier, a high accuracy attenuator, and the second output signal are selectively coupled so as to maintain the output ratio proportional to the input ratio.

44. A method according to claim 43, further including selectively coupling the high accuracy attenuator to the input of the low accuracy amplifier.

45. A method according to claim 43, further including selectively coupling the high accuracy attenuator to the output of the low accuracy amplifier.

46. A method according to claim 43, wherein the high accuracy attenuator comprises first and second high accuracy attenuator circuits, and the method further includes selectively coupling the first high accuracy attenuator circuit to the input of the low accuracy amplifier and selectively coupling the second high accuracy attenuator circuit to the output of the low accuracy amplifier circuit.

47. A method according to claim 43, further including providing the first input signal as the difference between input signals applied at least two distinct and different times.

48. A method according to claim 43, further including providing the second input signal as the difference between input signals applied at least two distinct and different times.

49. A method according to claim 43, further including operating storage circuitry so as to provide at substantially the same time output signals indicative of the first and second output signal.

50. A method according to claim 49, further including producing output signals during a time period distinct from the time periods during which the first and second input signals are selectively coupled.

51. A method according to claim 43, further including producing the input ratio and a digital output signal responsive to a third signal ratio.

52. A method according to claim 51, further including producing the digital output signal with a flash analog-to-digital conversion process.

53. A method according to claim 51, further including producing the digital output signal with a successive-approximation process.

54. A method according to claim 51, further including producing the input ratio from the third ratio by a method in accordance with claim 43.

55. A method according to claim 43, further including producing a digital output signal responsive to the output ratio.

56. A method according to claim 55, further including producing the digital output signal with a flash analog-to-digital conversion process.

57. A method according to claim 55, further including producing the digital output signal with a successive-approximation process.

58. A method according to claim 55, further including producing the input ratio from the third ratio by a method in accordance with claim 43.

59. A method of converting an analog input signal to a digital output signal, comprising:

operating a time multiplexer alternately in at least two time periods, wherein

(a) during a first time period connecting a first signal path of a first stage carrying an analog input signal to an input of an amplifier having a gain and connecting the output of the amplifier to a first signal path of a second stage, and

(b) during a second time period connecting a second signal path of the first stage carrying an analog reference signal to the input of the amplifier and connecting the output of the amplifier to a second signal path of the second stage;

wherein the analog input signal and analog reference signal are each amplified by the same gain as each is respectively transmitted from the first to the second stages during the first and second time periods.

60. A method according to claim 59, further including attenuating the analog reference signal in the second signal path of at least one of the stages.

61. A method according to claim 60, further including attenuating the analog reference signal in the second signal path of the first stage.

62. A method according to claim 60, further including attenuating the analog signal in the second signal path of the second stage.

63. A method according to claim 59, further including attenuating the analog reference signal in the second signal path of the first and second stages

64. A method according to claim 59, further including sampling and holding one of the analog signals in the second stage during one of the time periods so that it can be compared to the other of the analog signals in the next subsequent time period.

65. A method according to claim 64, wherein sampling and holding one of the analog signals is performed in one of the signal paths of the second stage.

66. A method according to claim 64, wherein sampling and holding one of the analog signals is performed in the second signal path of the second stage.

67. A method according to claim 65, wherein sampling and holding one of the analog signals is performed in the first signal path of the second stage.

68. A method according to claim 59, wherein sampling and holding one of the analog signals is performed in both the first and second signal paths of the second stage.

69. A method according to claim 59, further including operating at least one of the first and second stages in part as a flash analog-to-digital converter.

70. A method according to claim 59, further including operating at least one of the first and second stages in part as a successive-approximation converter.

71. A method according to claim 59, further including operating at least one of the first and second stages in part by methods in accordance with claim 59.

72. A method of converting an analog input signal to a digital output signal using a plurality of stages and an interstage amplifier disposed between each successive stage, comprising:

quantizing the analog input signal by comparing the input signal in the first stage and a residue signal in each subsequent stage with a reference signal provided to each stage, and

applying the same amplifier gain to the residue and reference signals provided to the subsequent stage.

73. A method according to claim 72, time multiplexing each interstage amplifier so as to amplify each residue and each reference signal provided to each subsequent stage

74. A method according claim 72, further including attenuating the reference signal provided to each subsequent stage.

75. A method according to claim 74, further including attenuating the reference signal prior to being provided to the interstage amplifier.

76. A method according to claim 74, further including attenuating the reference signal subsequent to being provided to the interstage amplifier.

77. A method according to claim 74, further including attenuate the reference signal prior to and subsequent to being provided to an interstage amplifier.

78. A method according to claim 72, further including sampling and holding the residue signal in each subsequent stage.

79. A method according to claim 72, further including sampling and holding the reference signal of each subsequent stage.

80. A method according to claim 72, further including sampling and holding the residue signal and reference signal of each subsequent stage.

81. A method according to claim 72, wherein the quantization in at least one of the plurality of stages is accomplished by a flash analog-to-digital conversion technique.

82. A method according to claim 72, wherein the quantization in at least one of the plurality of stages is accomplished by a successive-approximation technique.