Method and apparatus for protecting radio frequency power amplifiers

Abstract

A power amplifier protection system to sense one or more operating conditions of a power amplifier and regulate the power of the input signal to the power amplifier as a response to one or more of the sensed operating conditions. This dynamic protection system may protect a power amplifier from failure by monitoring such operating conditions as power output and temperature and reducing the amplitude of the input signal if the power amplifier is operating beyond specified levels.

What is claimed is: 
     
       1. A method for protecting a power amplifier comprising:
 sensing two or more operating conditions of a the power amplifier selected from the group consisting of temperature, current and output voltage; 
 comparing the sensed temperature, current, and output voltage operating conditions to specified operating limits for the a respective operating conditions; and 
 reducing the a power of an input signal to the power amplifier if one or more of the operating conditions is beyond specified operating limits for the power amplifier. 
 
     
     
       2. The method of  claim 1  wherein the current is the amplifier current. 
     
     
       3. The method of  claim 1  wherein the current is the current through a transistor in the amplifier. 
     
     
       4. A method for protecting a power amplifier comprising:
 sensing temperature, current and output voltage of the power amplifier; 
 comparing the sensed temperature, current, and output voltage operating conditions to specified operating limits for the respective operating conditions; and 
 reducing the a power of an input signal to the power amplifier if one or more of the operating conditions is beyond specified operating limits for the power amplifier. 
 
     
     
       5. The method of  claim 4  wherein the current is the amplifier current. 
     
     
       6. The method of  claim 4  wherein the current is the current through a transistor in the amplifier. 
     
     
       7. A power amplifier protection system comprising:
 a first sub-system to sense temperature, current, and output voltage operating conditions of a power amplifier; and 
 a second sub-system to regulate the a power of an input signal to the power amplifier in response to the sensed temperature, current, and output voltage operating conditions exceeding specified operating limits, respectively, and 
 a third sub-system to compare the sensed temperature, current, and output voltage operating conditions of the power amplifier to specified operating limits, respectively. 
 
     
     
       8. The method of claim 1 wherein the power amplifier comprises at least two amplifiers.  
     
     
       9. The method of claim 8 comprising a first amplifier within the at least two amplifiers, the first amplifier configured to receive the input signal of the power amplifier.  
     
     
       10. The method of claim 9 wherein the first amplifier is a variable gain amplifier coupled to receive the input signal.  
     
     
       11. The method of claim 8 comprising a first amplifier and a second amplifier within the at least two amplifiers, the first and second amplifiers coupled in series.  
     
     
       12. The method of claim 11 wherein the second amplifier is coupled to receive the input signal.  
     
     
       13. The method of claim 8 wherein the step of sensing two or more operating conditions of the power amplifier is performed on at least one sensing operation on an output signal of the power amplifier.  
     
     
       14. The method of claim 8 wherein the step of sensing two or more operating conditions of the power amplifier is performed on at least one sensing operation on an internal signal of the power amplifier.  
     
     
       15. The method of claim 8 wherein the power amplifier operates with a predetermined load impedance value.  
     
     
       16. The method of claim 8 further comprising a step of feeding back a plurality of values from the two or more sensed operating conditions, the plurality of fed back values being transmitted on at least two partially distinct feedback loop paths.  
     
     
       17. The method of claim 16 wherein the feedback loop is coupled between an output of the power amplifier and an initial stage of the power amplifier.  
     
     
       18. The method of claim 16 wherein the feedback loop is coupled between an output of the power amplifier and an intermediate stage of the power amplifier.  
     
     
       19. The method of claim 16 wherein current is sensed using a sensor selected from a group consisting of sense resistor, current mirror, an integrated current sensor and a voltage sensor that provides a voltage based on a sensed current.  
     
     
       20. The method of claim 16 further comprising a step of amplifying the plurality of fed back values using a plurality of amplifiers.  
     
     
       21. The method of claim 20 wherein an amplification across the plurality of amplifiers varies based on a signal magnitude of at least a first fed back value within the plurality of fed back values.  
     
     
       22. The method of claim 8 wherein the sensed temperature is detected internally within the power amplifier.  
     
     
       23. The method of claim 8 wherein at least one sensed operating condition is amplified and fed back to a first amplifier within the at least two amplifiers.  
     
     
       24. The method of claim 8 wherein the at least two amplifiers comprise a multi-stage power amplifier.  
     
     
       25. The method of claim 24 wherein the two or more sensed operating conditions are fed back within the multi-stage power amplifier, the two or more sensed operating conditions result in an adjustment to a gain value of a gain stage within the multi-stage power amplifier.  
     
     
       26. The method of claim 25 wherein the gain stage is an internal amplifier within the multi-stage power amplifier.  
     
     
       27. The method of claim 25 wherein the gain stage is a first amplifier within the multi-stage power amplifier.  
     
     
       28. The power amplifier protection system of claim 7 wherein the first sub-system, the second sub-system and the third sub-system are integrated within a multi-stage power amplifier.  
     
     
       29. The power amplifier protection system of claim 28 comprising a first amplifier within the multi-stage power amplifier, the first amplifier configured to receive the input signal of the power amplifier.  
     
     
       30. The power amplifier protection system of claim 29 wherein the first amplifier is a variable gain amplifier coupled to receive the input signal.  
     
     
       31. The power amplifier protection system of claim 28 comprising a first amplifier and a second amplifier within the multi-stage power amplifier, the first and second amplifiers coupled in series.  
     
     
       32. The power amplifier protection system of claim 31 wherein the second amplifier is coupled to receive the input signal.  
     
     
       33. The power amplifier protection system of claim 28 wherein the current is sensed on an internal signal of the power amplifier.  
     
     
       34. The power amplifier protection system of claim 28 wherein the multi-stage power amplifier operates with a predetermined load impedance value.  
     
     
       35. The power amplifier protection system of claim 28 further wherein the second and third sub-systems are integrated within a feedback loop controlling a gain of at least one amplifier within the multi-stage power amplifier.  
     
     
       36. The power amplifier protection system of claim 35 wherein the feedback loop is coupled between an output of the multi-stage power amplifier and an initial stage of the multi-stage power amplifier.  
     
     
       37. The power amplifier protection system of claim 35 wherein the feedback loop is coupled between an output of the multi-stage power amplifier and an intermediate stage of the multi-stage power amplifier.  
     
     
       38. The power amplifier protection system of claim 28 wherein current is sensed using a sensor selected from a group consisting of sense resistor, current mirror, an integrated current sensor and a voltage sensor that provides a voltage based on a sensed current.  
     
     
       39. The power amplifier protection system of claim 28 further comprising a plurality of amplifiers within a feedback loop coupled between an output of the multi-stage power amplifier and an initial stage of the multi-stage power amplifier, the feedback loop controlling at least one gain value associated with the multi-stage power amplifier.  
     
     
       40. The power amplifier protection system of claim 28 further comprising a plurality of amplifiers within a feedback loop coupled between an output of the multi-stage power amplifier and an intermediary stage of the multi-stage power amplifier, the feedback loop controlling at least one gain value associated with the multi-stage power amplifier.