Amplifier arrangement, and method for compensating for an offset

• US 7,304,534 B2
• Filed: 02/08/2006
• Issued: 12/04/2007
• Est. Priority Date: 02/18/2005
• Status: Expired due to Fees

• Current Assignee: Infineon Technologies AG
• Original Assignee: Infineon Technologies AG
• Inventors: Koller, Rainer, Wagenleitner, Thomas, Mutlu, Varol
• Primary Examiner(s): Choe; Henry
• Application Number:
  US11/350,224
• Publication Number:
  US 20060186954A1
• Time in Patent Office: 664 Days
• Field of Search: 330/9, 330/51, 330/149, 327/124, 327/307
• US Class Current: 330/9
• CPC Class Codes: H03F 1/34 Negative-feedback-circuit arrangements with or without positive feedback H03F1/02 - H03F1/30, H03F1/38 - H03F1/50, H03F3/50 take precedence ; for rejection of common mode signals H03F3/45479
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H03F 3/45475 using IC blocks as the active amplifying circuit
• CPC Class Codes: H03F 3/45968 by offset reduction
• CPC Class Codes: H03F 3/45977 using switching means, e.g. sample and hold

Abstract

An amplifier arrangement and a method for compensating for an offset in an amplifier is provided. A respective switch for connecting together the inputs in a compensation operating mode and for interrupting the feedback path in this operating mode is provided in an amplifier. A control device detects an output signal and drives a controllable current source, which can be coupled to one of the two inputs of the amplifier, in such a manner that a compensation current which minimizes the offset is provided. The arrangement and method can be used, for example, in transmission arrangements.

Claims

1. An amplifier arrangement, comprising:

an amplifier comprising two inputs and an output;

a feedback path coupled between the output and at least one of the two inputs;

a first switch configured to selectively couple the two inputs to one another in a compensation operating mode;

a second switch configured to selectively interrupt the feedback path in the compensation operating mode;

a controllable current source coupled to at least one of the two inputs of the amplifier; and

a control device configured to control the first and second switches and the controllable current source in the compensation operating mode based on the output of the amplifier to reduce an offset at the inputs of the amplifier by providing a compensation current via the controllable current source to the at least one of the two inputs.

2. The amplifier arrangement of claim 1, wherein the controllable current source comprises a plurality of current sources coupled together in parallel that are configured to be selectively connected and disconnected independently of one another based on the control device.

3. The amplifier arrangement of claim 1, wherein controllable current source comprises a plurality of current sources coupled together in parallel that are configured to be selectively connected and disconnected independently of one another based on the control device, and wherein the plurality of current sources provide current values that are graduated in binary fashion.

4. The amplifier arrangement of claim 1, wherein the controllable current source is integral within the amplifier.

5. The amplifier arrangement of claim 1, further comprising another controllable current source coupled to the other input of the amplifier, and to the control device, and configured to generate a compensation current based on the control device.

6. The amplifier arrangement of claim 1, wherein the control device is configured to reduce the offset by means of altering a current produced by the controllable current source iteratively via successive approximation.

7. The amplifier arrangement of claim 1, wherein the amplifier comprises a supply potential connection and a reference potential connection.

8. The amplifier arrangement of claim 1, wherein the amplifier comprises a differential amplifier.

9. The amplifier arrangement of claim 1, wherein the amplifier comprises an operational amplifier.

10. The amplifier arrangement of claim 1, wherein the amplifier is connected to one or more additional components in the feedback path to form a filter.

11. A method for compensating for an offset in an amplifier, comprising:

interrupting a feedback path of the amplifier from an output to at least one input of the amplifier;

coupling two inputs of the amplifier to one another;

detecting an output signal from the amplifier indicative of the offset; and

providing a controllable compensation current at one of the inputs of the amplifier based on the detected output signal.

12. The method of claim 11, wherein the controllable compensation current is adjusted iteratively via successive approximation.

13. The method of claim 11, wherein detecting the output signal from the amplifier comprises determining whether the output signal corresponds to a supply potential or to a reference potential associated with the amplifier.

14. The method of claim 11, wherein detecting the output signal from the amplifier comprises detecting a change in the output signal between a supply potential and a reference potential.

15. The method of claim 11, wherein coupling the two inputs of the amplifier to one another comprises coupling together input terminals of a functional block upstream of the amplifier in order to compensate for an offset in the amplifier and the upstream functional. block.

16. A communications transmission arrangement, comprising:

a baseband module configured to generate in-phase and quadrature signals associated with a desired communication transmission;

a radio frequency module configured to receive the in-phase and quadrature signals, and transform such signals into a radio frequency transmission signal, the radio frequency module comprising an amplifier arrangement at an input thereof associated with the in-phase and quadrature signals, respectively;

input switches configured to selectively short one or more inputs associated with either the baseband module or the radio frequency module during a compensation mode;

a control device configured to close the input switches, place the amplifier arrangement into an open-loop configuration, and evaluate an output condition of the amplifier arrangement during the compensation mode;

a controllable current source configured to provide a variable compensation current to the amplifier arrangement to reduce an offset thereof based on the control device in the compensation mode.

17. The transmission arrangement of claim 16, wherein the controllable current source comprises a plurality of current sources selectively coupled together in parallel based on the control device, thereby configured to selectively provide a plurality of different current values.

18. The transmission arrangement of claim 17, wherein the control device is configured to iteratively alter an amount of current associated with the controllable current source until an output condition of the amplifier arrangement changes in the compensation mode.

19. The transmission arrangement of claim 18, further comprising a memory configured to store an offset current compensation value, and wherein the control device is further configured to ascertain the offset current compensation value based on the output of the amplifier arrangement after multiple iterations in the compensation mode, and send the ascertained offset current compensation value to the memory in the compensation mode.

20. The transmission arrangement of claim 19, wherein the control device is further configured to retrieve the offset current compensation value from the memory, and employ the value to control the controllable current source during a normal signal transmission mode.