TMR/GMR amplifier with input current compensation

• US 7,751,140 B1
• Filed: 10/22/2007
• Issued: 07/06/2010
• Est. Priority Date: 08/30/2004
• Status: Expired due to Fees

• Current Assignee: Marvell International Limited (Marvell Technology Group Limited)
• Original Assignee: Marvell International Limited (Marvell Technology Group Limited)
• Inventors: Voo, Thart Fah
• Primary Examiner(s): NEGRON, DANIELL L
• Application Number:
  US11/975,805
• Time in Patent Office: 988 Days
• Field of Search: None
• US Class Current: 360/67
• CPC Class Codes: G11B 2005/0018 by current biasing control or regulation
• CPC Class Codes: G11B 5/02 Recording, reproducing, or erasing methods; Read, write or erase circuits therefor
• CPC Class Codes: H03F 1/342 in field-effect transistor amplifiers
• CPC Class Codes: H03F 2200/144 the feedback circuit of the amplifier stage comprising a passive resistor and passive capacitor
• CPC Class Codes: H03F 2200/453 Controlling being realised by adding a replica circuit or by using one among multiple identical circuits as a replica circuit
• CPC Class Codes: H03F 2200/474 A current mirror being used as sensor
• CPC Class Codes: H03F 2203/45136 One differential amplifier in IC-block form being shown
• CPC Class Codes: H03F 2203/45528 the FBC comprising one or more passive resistors and being coupled between the LC and the IC
• CPC Class Codes: H03F 3/45475 using IC blocks as the active amplifying circuit

Abstract

A system includes an amplifier and a feedback network that includes a first resistance having one end that communicates with an input of the amplifier and an opposite end that communicates with an output of the amplifier. A first replica circuit provides a replica of a DC characteristic at the output of the amplifier. A second replica circuit provides a replica of a DC characteristic at the input of the amplifier. An input of a first buffer communicates with the first replica circuit, and an input of a second buffer communicates with the second replica circuit. A second resistance communicates with an output of the first buffer and an output of the second buffer. A first current source provides a first current at the input of the amplifier that is proportional to a second current flowing through the second resistance.

Claims

1. A system comprising:

an amplifier;

a feedback network that includes a first resistance having one end that communicates with an input of the amplifier and an opposite end that communicates with an output of the amplifier;

a first replica circuit that provides a replica of a DC characteristic at the output of the amplifier;

a second replica circuit that provides a replica of a DC characteristic at the input of the amplifier;

first and second buffers, wherein an input of the first buffer communicates with the first replica circuit, and an input of the second buffer communicates with the second replica circuit;

a second resistance that communicates with an output of the first buffer and an output of the second buffer; and

a first current source that provides a first current at the input of the amplifier that is proportional to a second current flowing through the second resistance.

2. The system of claim 1 wherein the second resistance has a resistance value that is approximately equal to a resistance value of the first resistance, and wherein the first current is approximately equal to the second current.

3. The system of claim 1 wherein at least one of the first and second replica circuits and the first and second buffers operate on standby power when power to the amplifier is turned off.

4. The system of claim 1 further comprising:

a second current source; and

a first variable resistance that is biased by the second current source, wherein the input of the amplifier communicates with the first variable resistance.

5. The system of claim 4 wherein the second replica circuit comprises:

a third current source that provides current that is proportional to current provided by the second current source; and

a second variable resistance that is biased by the third current source.

6. The system of claim 1 further comprising a second current source that provides a third current at the output of the amplifier that is approximately equal to the first current.

7. The system of claim 6 further comprising:

a third current source; and

a variable resistance that is biased by the third current source, wherein the input of the amplifier communicates with the variable resistance.

8. The system of claim 1 wherein the amplifier is arranged in a differential mode.

9. The system of claim 1 wherein the amplifier is arranged in a single-ended mode.

10. The system of claim 1 further comprising a DC blocking capacitance that communicates with the input of the amplifier.

11. A method comprising:

providing a feedback network that includes a first resistance having one end that communicates with an input of an amplifier and an opposite end that communicates with an output of the amplifier;

providing a replica of a DC characteristic of the output of the amplifier using a first replica circuit;

providing a replica of a DC characteristic at the input of the amplifier using a second replica circuit;

coupling an input of a first buffer with the first replica circuit and an input of a second buffer with the second replica circuit;

providing a second resistance that communicates with an output of the first buffer and an output of the second buffer; and

supplying a first current at the input of the amplifier that is proportional to a second current flowing through the second resistance.

12. The method of claim 11 wherein the second resistance has a resistance value that is approximately equal to a resistance value of the first resistance, and wherein the first current is approximately equal to the second current.

13. The method of claim 11 further comprising operating the first and second replica circuits and the first and second buffers on standby power when power to the amplifier is turned off.

14. The method of claim 11 further comprising:

providing a first current source; and

providing a first variable resistance that is biased by the first current source, wherein the input of the amplifier communicates with the first variable resistance.

15. The method of claim 14 further comprising:

providing a second current source that provides current that is proportional to current provided by the first current source; and

providing a second variable resistance that is biased by the second current source.

16. The method of claim 11 further comprising providing a third current at the output of the amplifier that is approximately equal to the first current.

17. The method of claim 11 further comprising arranging the amplifier in a differential mode.

18. The method of claim 11 further comprising arranging the amplifier in a single-ended mode.

19. The method of claim 11 further comprising providing a DC blocking capacitance that communicates with the input of the amplifier.