Method and system for canceling feedback current in an amplifier system

• US 7,881,001 B1
• Filed: 08/15/2008
• Issued: 02/01/2011
• 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): Negrón; Daniell L.
• Application Number:
  US12/228,742
• Time in Patent Office: 900 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 method for providing feedback current cancellation comprises providing an amplifier with an input, an output, and at least one stage, feeding back a first current based on the output of the amplifier to the input of the amplifier, and substantially cancelling the first current by supplying a second current to the input of the amplifier.

Claims

1. A method for providing feedback current cancellation, the method comprising:

providing an amplifier with an input, an output, and at least one stage;

receiving an input signal at the input of the amplifier;

feeding back a first current based on the output of the amplifier to the input of the amplifier;

feeding back a second current to the output of the amplifier;

substantially cancelling the first current by supplying a third current to the input of the amplifier; and

substantially cancelling the second current by supplying a fourth current to the output of the amplifier.

2. The method of claim 1 further comprising arranging the amplifier in a differential mode.

3. The method of claim 1 further comprising arranging the amplifier in a single-ended mode.

4. The method of claim 1 further comprising performing DC signal blocking at the input of the amplifier.

5. A method for providing a sensor system, the method comprising:

providing an amplifier with an input, an output, and at least one stage;

receiving an input signal at the input of the amplifier;

feeding back a first current based on the output of the amplifier to the input of the amplifier;

substantially cancelling the first current by supplying a second current to the input of the amplifier;

coupling a variable resistance to the input of the amplifier; and

biasing the variable resistance with a current source.

6. The method of claim 5 further comprising:

feeding back a third current to the output of the amplifier; and

substantially cancelling the third current by providing a fourth current at the output of the amplifier.

7. The method of claim 5 further comprising arranging the amplifier in a differential mode.

8. The method of claim 5 further comprising arranging the amplifier in a single-ended mode.

9. The method of claim 5 further comprising performing DC signal blocking at the input of the amplifier.

10. A method for cancelling feedback current that flows from an output of an amplifier to an input of the amplifier, the feedback current being caused by a feedback network having a first terminal coupled to the output of the amplifier and having a second terminal coupled to the input of the amplifier, the method comprising:

amplifying a signal received at the input of the amplifier to form an amplified signal at the output of the amplifier;

generating a first current through a feedback current cancellation module coupled to the amplifier;

providing the first current to the input of the amplifier to cancel the feedback current at the input of the amplifier; and

providing an opposite of the first current to the output of the amplifier.

11. The method of claim 10, wherein:

amplifying a signal comprises amplifying a signal received from an input device; and

providing the first current to the input of the amplifier to cancel the feedback current at the input of the amplifier prevents the feedback current from passing back to the input device.

12. The method of claim 11, wherein providing the first current to the input of the amplifier to cancel the feedback current at the input of the amplifier further prevents the feedback current from altering performance of the amplifier.

13. The method of claim 10, wherein providing the opposite of the first current to the output of the amplifier permits the feedback network to draw no current from the output of the amplifier.

14. The method of claim 10, wherein the amplifier comprises a single-ended amplifier.

15. The method of claim 14, wherein the single-ended amplifier includes multiple stages.

16. The method of claim 10, wherein the amplifier comprises a differential amplifier.

17. The method of claim 10, further comprising performing DC signal blocking at the input of the amplifier.

18. The method of claim 10, wherein the feedback current cancellation module does not share any components with the feedback network.