Analog-digital converter with gain adjustment for high-speed operation

• US 20050237234A1
• Filed: 02/03/2005
• Published: 10/27/2005
• Est. Priority Date: 02/05/2004
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Inventors: Kobayashi, Shigeto, Tani, Kuniyuki, Wada, Atsushi, Kojima, Noriaki
• Granted Patent: US 7,289,055 B2
• Time in Patent Office: Days
• US Class Current: 341/155
• CPC Class Codes: H03M 1/14 Conversion in steps with each step involving the same or a different conversion means and delivering more than one bit
• CPC Class Codes: H03M 1/162 the steps being performed sequentially in a single stage, i.e. recirculation type H03M1/161 takes precedence
• CPC Class Codes: H03M 1/167 all stages comprising simultaneous converters H03M1/165 takes precedence

Abstract

An input analog signal is fed to an amplifier circuit and an AD converter circuit. The AD converter circuit converts the input analog signal into a digital value of a predetermined number of bits, and outputs the digital value to an encoder (not shown) A DA converter circuit converts the digital value of a predetermined number of bits output from the AD converter circuit into an analog signal. The amplifier circuit samples and amplifies the input analog signal by a factor of α (greater than 1). A subtracter circuit subtracts an output of the DA converter circuit amplified by a factor of α from an output of the amplifier circuit.

Claims

1. An analog-digital converter comprising:

an AD converter circuit converting an input analog signal into a digital value of a predetermined number of bits;

a DA converter circuit converting an output of said AD converter circuit into an analog signal;

a first amplifier circuit provided parallel with said AD converter circuit and amplifying said input analog signal by a predetermined gain;

a subtracter circuit subtracting an output of said DA converter circuit, amplified by a gain practically identical to the gain of said first amplifier circuit, from an output of said first amplifier circuit; and

a second amplifier circuit amplifying an output of said subtracter circuit and feeding the amplified output back to inputs of said AD converter circuit and said first amplifier circuit.

2. The analog-digital converter according to claim 1, wherein an amplifying gain of a system comprising said AD converter and said DA converter circuit is practically identical to the gain of said first amplifier.

3. The analog-digital converter according to claim 1, wherein a ratio between a reference voltage range accommodating a reference potential of said DA converter circuit and a reference voltage range accommodating a reference potential of said AD converter circuit is set in accordance with said predetermined gain.

4. The analog-digital converter according to claim 2, wherein a ratio between a reference voltage range accommodating a reference potential of said DA converter circuit and a reference voltage range accommodating a reference potential of said AD converter circuit is set in accordance with said predetermined gain.

5. The analog-digital converter according to claim 1, wherein said subtracter circuit and said second amplifier circuit are an integral subtracting amplifier circuit, said integral subtracting amplifier circuit amplifying the output of said AD converter circuit by a gain which is practically identical to the gain of said first amplifier circuit, and amplifying a result of subtraction from the output of said first amplifier circuit.

6. The analog-digital converter according to claim 5, wherein said integral subtracting amplifier circuit includes an operational amplifier, a first terminal for receiving the output of said first amplifier circuit and a second terminal for receiving the output of said DA converter circuit being connected to said operational amplifier, and a ratio between a capacitance connected between said second terminal and said DA converter circuit and a capacitance connected between said first terminal and said first amplifier circuit being set in accordance with said predetermined gain.

7. An analog-digital converter comprising:

an AD converter circuit converting an input analog signal into a digital value of a predetermined number of bits;

a DA converter circuit converting an output of said AD converter circuit into an analog signal;

a first amplifier circuit provided parallel with said AD converter circuit and amplifying said input analog signal by a first gain;

a subtracter circuit subtracting an output of said DA converter circuit, amplified by a gain practically identical to the gain of said first amplifier circuit, from an output of said first amplifier circuit; and

a second amplifier circuit amplifying an output of said subtracter circuit by a second gain and feeding the amplified output back to said AD converter circuit, wherein

a total gain, which is a product of said first gain and said second gain, represents a required gain, and said first gain is greater than 1 and equal to or smaller than said second gain.

8. The analog-digital converter according to claim 7, wherein said first gain is equal to or less than ½

of said second gain.

9. The analog-digital converter according to claim 7, wherein said first gain of said first amplifier circuit is set to a maximum value that permits any input signal in a desired input voltage range to produce an output fitted in an output voltage range, and said second gain is set to a value which is responsible for the remainder of said required gain.

10. An analog-digital converter of a pipeline type comprising a plurality of stages, wherein at least one of said plurality of stages is a cyclic stage that includes the analog-digital converter according to claim 7.

11. An analog-digital converter of a pipeline type comprising a plurality of stages, wherein at least one of said plurality of stages is a cyclic stage that includes the analog-digital converter according to claim 8.

12. An analog-digital converter of a pipeline type comprising a plurality of stages, wherein at least one of said plurality of stages is a cyclic stage that includes the analog-digital converter according to claim 9.

13. The analog-digital converter according to claim 7, wherein said first gain is 2.

14. An analog-digital converter comprising:

an AD converter circuit converting an input analog signal into a digital value of a predetermined number of bits;

a DA converter circuit converting an output of said AD converter circuit into an analog signal;

a first amplifier circuit provided parallel with said AD converter circuit and amplifying said input analog signal by a first gain;

a subtracter circuit subtracting an output of said DA converter circuit, amplified by a gain practically identical to the gain of said first amplifier circuit, from an output of said first amplifier circuit; and

a second amplifier circuit amplifying an output of said subtracter circuit by a second gain and feeding the amplified output back to said AD converter circuit, wherein a total gain, which is a product of said first gain and said second gain, represents a required gain, and the first gain is set to a value close to said second gain.

15. The analog-digital converter according to claim 14, wherein said first gain and said second gain are related to each other such that one is equal to or more than ½

of the other and equal to or less than twice the other.

16. The analog-digital converter according to claim 14, wherein said first gain and said second gain are practically identical with each other.

17. The analog-digital converter according to claim 15, wherein said first gain-and said second gain are practically identical with each other.

18. An analog-digital converter of a pipeline type comprising a plurality of stages, wherein at least one of said plurality of stages is a cyclic stage that includes the analog-digital converter according to claim 14.

19. An analog-digital converter of a pipeline type comprising a plurality of stages, wherein at least one of said plurality of stages is a cyclic stage that includes the analog-digital converter according to claim 15.

20. An analog-digital converter of a pipeline type comprising a plurality of stages, wherein at least one of said plurality of stages is a cyclic stage that includes the analog-digital converter according to claim 16.

21. An analog-digital converter of a pipeline type comprising a plurality of stages, wherein at least one of said plurality of stages is a cyclic stage that includes the analog-digital converter according to claim 17.

22. The analog-digital converter according to claim 14, wherein said first gain is 2.

23. An analog-digital converter converting an input analog signal into a digital signal of a plurality of bits in a plurality of stages, comprising a plurality of amplifier circuits, wherein two or more of said amplifier circuits with practically the same gain are differently designed in respect of at least one of a circuit constant and a circuit configuration.

24. The analog-digital converter according to claim 23, wherein at least one of the circuit constant and the circuit configuration of the amplifier circuit which first receives said input analog signal is of a higher specification than the corresponding specification of the other amplifier circuits.

25. The analog-digital converter according to claim 23, wherein at least one of the circuit constant and the circuit configuration of an amplifier circuit, upstream in a plurality of amplifier circuits transmitting an input analog signal, is of a higher specification than that of the amplifier circuits downstream in the order of transmission.

26. The analog-digital converter according to claim 23, wherein said plurality of amplifier circuits include an operational amplifier as a constituting element, and the circuit configuration of said operational amplifier differs between said amplifier circuits with practically the same gain.

27. The analog-digital converter according to claim 23, wherein each of said plurality of amplifier circuits is embodied by a switched capacitor operational amplifier, and the switched capacitor operational amplifier includes an operational amplifier, at least one first capacitance connected to an input terminal of said operational amplifier and at least one second capacitance connected between the input terminal and an output terminal of said operational amplifier, and values of said first capacitance and said second capacitance differ between said amplifiers with practically the same gain.

28. The analog-digital converter according to claim 23, further comprising a plurality of stages converting an input analog signal into a digital value of a predetermined number of bits, wherein at least one of said plurality of stages includes an amplifier circuit selected from said plurality of amplifier circuits, the amplifier circuit amplifying a difference between said input analog signal and a signal derived by conversion from a digital value, obtained by analog-to-digital conversion in the stage in which the amplifier circuit is provided, into an analog signal, and feeding back the amplified difference to an input of the stage.

29. The analog-digital converter according to claim 23, further comprising a plurality of stages converting an input analog signal into a digital value of a predetermined number of bits, wherein at least one of said plurality of stages includes two amplifier circuits selected from said plurality of amplifier circuits, a first amplifier circuit of said two amplifier circuits amplifying said input analog signal by a first predetermined gain, and a second amplifier circuit of said two amplifier circuits amplifying, by a second predetermined gain, a difference between an analog signal output from said first amplifier circuit and a signal derived by conversion from a digital value, obtained by analog-to-digital conversion in a stage in which said second amplifier circuit is provided, into an analog signal amplified by practically the same gain as said first predetermined gain, and feeding back the amplified difference to an input of the stage.

30. The AD converter according to claim 23, further comprising:

an AD converter circuit converting an input analog signal into a digital value of a predetermined number of bits, and

a DA converter circuit converting an output of said AD converter circuit into an analog signal, wherein

a first amplifier circuit of said plurality of amplifier circuits amplifies said input analog signal by a first predetermined gain, and a second amplifier circuit of said plurality of amplifier circuits amplifies, by a second predetermined gain, a difference between an analog signal output from said first amplifier circuit and an analog signal output from said DA converter circuit, amplified by practically the same gain as said first predetermined gain, and outputs the amplified difference to said AD converter circuit and said first amplifier circuit.