Circuit and method of establishing DC bias levels in an RF power amplifier

• US 20050134376A1
• Filed: 12/22/2003
• Published: 06/23/2005
• 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.
• Granted Patent: US 7,064,605 B2
• Time in Patent Office: Days
• 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 3/189 High-frequency amplifiers, e.g. radio frequency amplifiers
• 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 establishing DC bias levels in an RF power amplifier having multiple power amplifier stages, comprising:

generating a feedback signal using the input and output of a first power amplifier stage; and

using the feedback signal to control the DC bias level of a second power amplifier stage.

2. The method of claim 1, wherein the DC bias level is generated to cause the DC levels at the input and output of the first power amplifier stage to have a predetermined relationship.

3. The method of claim 1, wherein the DC bias level is generated to cause the DC levels at the input and output of the first power amplifier stage to be approximately equal.

4. The method of claim 1, wherein the feedback signal is generated based on the DC level at the input and output of the first power amplifier stage.

5. The method of claim 3, wherein the feedback signal is generated by comparing the DC levels at the input and output of the first power amplifier stage.

6. The method of claim 3, wherein the feedback signal is used to set the DC levels at the input and output of the first power amplifier stage to approximately half of the supply voltage.

7. The method of claim 1, wherein the RF power amplifier comprises a non-linear power amplifier.

8. The method of claim 1, wherein the second power amplifier stage comprises a predriver circuit.

9. The method of claim 1, wherein the second power amplifier stage is adapted to receive an RF input signal.

10. A method of establishing DC bias levels in an RF power amplifier having multiple power amplifier stages, comprising:

sensing the DC bias level at the input and at the output of a first power amplifier stage;

generating a feedback signal using sensed DC bias levels; and

coupling the feedback signal to a second power amplifier stage to control the DC bias level of the second power amplifier stage.

11. The method of claim 10, wherein the DC bias level is generated to cause the DC levels at the input and output of the first power amplifier stage to have a predetermined relationship.

12. The method of claim 10, wherein the DC bias level is generated to cause the DC levels at the input and output of the first power amplifier stage to be approximately equal.

13. The method of claim 10, wherein the feedback signal is generated by comparing the DC levels at the input and output of the first power amplifier stage.

14. The method of claim 10, wherein the feedback signal is used to set the DC levels at the input and output of the first power amplifier stage to approximately half of the supply voltage.

15. The method of claim 10, wherein the RF power amplifier comprises a non-linear power amplifier.

16. The method of claim 10, wherein the second power amplifier stage comprises a predriver circuit.

17. The method of claim 10, wherein the second power amplifier stage is adapted to receive an RF input signal.

19. An RF power amplifier comprising:

a first power amplifier stage;

a second power amplifier stage; and

an amplifier having a first input coupled to the output of the first power amplifier stage, a second input coupled to the input of the first power amplifier stage for sensing the DC bias levels at the input and output of the first power amplifier stage, and an output coupled to the second power amplifier stage to control the DC bias level of the second power amplifier stage.

20. The RF power amplifier of claim 19, wherein the DC bias level is generated so as to cause the DC levels at the input and output of the first power amplifier stage to have a predetermined relationship.

21. The RF power amplifier of claim 19, wherein the DC bias level is generated so as to cause the DC levels at the input and output of the first power amplifier stage to be approximately equal.

22. The RF power amplifier of claim 19, wherein the feedback signal is generated based on the DC level at the input and output of the first power amplifier stage.

23. The RF power amplifier of claim 22, wherein the feedback signal is generated by comparing the DC levels at the input and output of the first power amplifier stage.

24. The RF power amplifier of claim 19, wherein the feedback signal is used to set the DC levels at the input and output of the first power amplifier stage to approximately half of the supply voltage.

25. The RF power amplifier of claim 19, wherein the second power amplifier stage is adapted to receive an RF input signal.