Amplifying signals using positive envelope feedback

Abstract

Described herein are methods for amplifying radio-frequency signals using power amplifier (PA) architectures that improve PA performance (e.g., efficiency, linearity, etc.) over an extended range of the operating power levels of the PA. These methods can use positive envelope feedback to dynamically adjust a bias to a stage of the amplification chain. The methods improve amplification processes with little additional complexity, little additional current consumption, and/or little additional chip area relative to other typical amplification methods. The methods utilize a dynamic biasing technique using positive envelope feedback based at least in part on an instantaneous envelope signal at an output of a power amplifier.

What is claimed is: 
     
         1 . A method for amplifying radio-frequency signals, the method comprising:
 amplifying, using a driver stage of a multi-stage amplifier, an input signal to generate an amplified driver signal;   amplifying, using a power stage of the multi-stage amplifier, the amplified driver signal to generating an amplified output signal;   detecting an envelope of the amplified output signal;   generating a dynamic bias signal based on the detected envelope;   biasing the power stage with the dynamic bias signal.   
     
     
         2 . The method of  claim 1  wherein generating the dynamic bias signal includes scaling an envelope signal that corresponds to the envelope of the amplified output signal. 
     
     
         3 . The method of  claim 2  wherein generating the dynamic bias signal further comprises offsetting the scaled envelope signal using a DC signal. 
     
     
         4 . The method of  claim 3  wherein scaling the envelope signal comprises using a voltage divider to generate the scaled envelope signal. 
     
     
         5 . The method of  claim 3  wherein the DC signal corresponds to a quiescent biasing condition of the multi-stage amplifier. 
     
     
         6 . The method of  claim 1  wherein biasing the power stage includes providing the dynamic bias signal to a gate of a power stage transistor. 
     
     
         7 . The method of  claim 1  wherein detecting the envelope of the amplified output signal includes receiving the amplified output signal from the power stage. 
     
     
         8 . The method of  claim 7  wherein detecting the envelope of the amplified output signal does not rely on signal flow through biasing circuits of the multi-stage amplifier. 
     
     
         9 . The method of  claim 1  wherein the dynamic bias signal corresponds to an instantaneous output power of the multi-stage amplifier. 
     
     
         10 . The method of  claim 9  wherein the dynamic bias signal comprises a scaled and DC-offset voltage corresponding to a continuously varying function of the instantaneous output power. 
     
     
         11 . A method for biasing a multi-stage amplifier, the method comprising:
 detecting an envelope of an amplified output signal using a signal path from an output of the multi-stage amplifier;   generating an envelope signal corresponding to the detected envelope, the envelope signal corresponding to an instantaneous power of the amplified output signal;   generating a dynamic bias signal based on the envelope signal such that an increase in amplitude of the amplified output signal results in increasing the dynamic bias signal; and   directing the dynamic bias signal to the multi-stage amplifier.   
     
     
         12 . The method of  claim 11  wherein generating the dynamic bias signal includes scaling the envelope signal using a voltage divider. 
     
     
         13 . The method of  claim 12  wherein generating the dynamic bias signal includes adjusting an offset of the scaled envelope signal using a DC voltage. 
     
     
         14 . The method of  claim 11  wherein the multi-stage amplifier includes one or more transistors at a final amplification stage. 
     
     
         15 . The method of  claim 14  wherein the dynamic bias signal is directed to a gate of the one or more transistors of the final amplification stage. 
     
     
         16 . The method of  claim 11  wherein the dynamic bias signal is proportional to the envelope signal. 
     
     
         17 . The method of  claim 11  wherein the dynamic bias signal is greater than or equal to a threshold bias value. 
     
     
         18 . The method of  claim 17  wherein generating the dynamic bias signal includes, responsive to the envelope signal being less than the threshold bias value, providing a signal equal to the threshold bias value. 
     
     
         19 . The method of  claim 18  wherein generating the dynamic bias signal includes, responsive to the envelope signal being greater than the threshold bias value, providing a signal that is proportional to the envelope signal. 
     
     
         20 . The method of  claim 11  wherein directing the dynamic bias signal includes directing the dynamic bias signal to a final amplification stage of the multi-stage amplifier.