Circuit and method of reducing noise in an RF power amplifier

• US 7,212,070 B2
• Filed: 12/22/2003
• Issued: 05/01/2007
• Est. Priority Date: 12/22/2003
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Silicon Laboratories Incorporated
• Inventors: Westwick, Alan L., Paul, Susanne A.
• Primary Examiner(s): NGUYEN, PATRICIA T
• Application Number:
  US10/743,217
• Publication Number:
  US 20050134375A1
• Time in Patent Office: 1,226 Days
• Field of Search: 330/98, 330/269, 330/277, 330/253
• US Class Current: 330/98
• CPC Class Codes: H03F 1/30 Modifications of amplifiers to reduce influence of variations of temperature or supply voltage or other physical parameters in differential amplifiers H03F3/45479
• CPC Class Codes: H03F 3/45941 Controlling the input circuit of the differential amplifier

Abstract

A method and apparatus is used to provide DC stabilization and noise reduction in a multistage power amplifier. The invention uses various feedback techniques to stabilize DC levels, which helps to reduce noise. The invention also uses other techniques to reduce noise, and to reduce the noise transfer function in a power amplifier.

Claims

1. A method of reducing noise in a multi-stage power amplifier, comprising:

providing a first power amplifier stage having an inductance coupled to a first switching device;

coupling a second power amplifier stage to the first power amplifier stage, wherein the second power amplifier stage has an inductance coupled to a second switching device; and

providing a feedback path from the second power amplifier stage to the first power amplifier stage to force the DC levels of the first and second power amplifier stages to be approximately equal, wherein the feedback path is provided by coupling an inductor to each of the inductances of the first and second power amplifier stages.

2. The method of claim 1, wherein the feedback path is provided by two inductors.

3. A method of reducing noise in a multi-stage power amplifier, comprising:

providing a first power amplifier stage having an inductance coupled between first and second switching devices;

providing a second power amplifier stage having an inductance coupled between third and fourth switching devices; and

forming a feedback path from the second power amplifier stage to the first power amplifier stage to force the DC levels of the first and second power amplifier stages to be approximately equal, wherein the feedback path is provided by an inductor.

4. The method of claim 3, wherein the feedback path is formed by coupling an inductor to each of the inductances.

5. A multi-stage power amplifier comprising:

a first power amplifier stage having an inductance coupled to a first switching device;

a second power amplifier stage having an inductance coupled to a second switching device; and

a feedback path coupled between the second and first power amplifier stages so as to make the DC levels of the first and second power amplifier stages to be approximately equal, wherein the feedback path is formed by coupling an inductor to each of the inductances.

6. A method of reducing noise in a multi-stage power amplifier, comprising:

providing a first power amplifier stage having an inductance coupled to a first switching device;

coupling a second power amplifier stage to the first power amplifier stage, wherein the second power amplifier stage has an inductance coupled to a second switching device; and

providing a feedback path from the second power amplifier stage to the first power amplifier stage to force the DC levels of the first and second power amplifier stages to be approximately equal, wherein the feedback path is provided by an amplifier coupled to each of the inductances of the first and second power amplifier stages.

7. The method of claim 6, wherein the amplifier comprises an op -amp.

8. A multi-stage power amplifier comprising:

a first power amplifier stage having an inductance coupled to a first switching device;

a second power amplifier stage having an inductance coupled to a second switching device; and

a feedback path coupled between the second and first power amplifier stages so as to make the DC levels of the first and second power amplifier stages to be approximately equal, wherein the feedback path is formed by coupling an amplifier between the second and first power amplifier stages, wherein the amplifier is coupled to each of the inductances of the first and second power amplifier stages.

9. The multi-stage power amplifier of claim 8, wherein the feedback path is formed by coupling an op-amp between the second and first power amplifier stages.

10. A method of reducing noise in a multi-stage power amplifier, comprising:

providing a first power amplifier stage having an inductance coupled to a first switching device;

coupling a second power amplifier stage to the first power amplifier stage, wherein the second power amplifier stage has an inductance coupled to a second switching device; and

providing a feedback path from the second power amplifier stage to the first power amplifier stage to force the DC levels of the first and second power amplifier stages to be approximately equal, wherein the feedback path is provided by two inductors.

11. The method of claim 10, wherein the feedback path is provided by coupling the two inductors to the inductances of the first and second power amplifier stages.