Doherty amplifier

Abstract

A multistage linear power amplifier receiving an input signal. The multistage linear power amplifier comprises a plurality of Class-AB amplifiers connected in a cascade configuration. The plurality of Class-AB amplifiers amplifies the input signal to generate an amplified input signal. At least one of the plurality of Class-AB amplifiers is biased such that the multistage linear power amplifier emulates a Class-C amplifier.

1 - 19 . (canceled) 
     
     
         20 . A multistage power amplifier comprising:
 a plurality of amplifiers biased within a bias range associated with an amplifier of a first class, at least one of the plurality of amplifiers biased within the bias range is biased within a first portion of the bias range and at least one other of the plurality of amplifiers biased within the bias range is biased within a second portion of the bias range that differs from the first portion of the bias range such that the multistage power amplifier mimics a behavior of an amplifier of a second class while each of the plurality of power amplifiers is biased within the bias range associated with the amplifier of the first class.   
     
     
         21 . The multistage amplifier of  claim 20  wherein the plurality of amplifiers are connected in series. 
     
     
         22 . The multistage amplifier of  claim 20  wherein amplifiers of the first class exhibit a different linearity than amplifiers of the second class. 
     
     
         23 . The multistage amplifier of  claim 20  wherein amplifiers of the second class exhibit different power added efficiency than amplifiers of the first class. 
     
     
         24 . The multistage amplifier of  claim 20  wherein the amplifier of the first class is a Class-AB amplifier and the amplifier of the second class is a Class-C amplifier. 
     
     
         25 . The multistage amplifier of  claim 20  wherein amplifiers of the first class exhibit greater linearity and lower power added efficiency than amplifiers of the second class. 
     
     
         26 . A Doherty power amplifier comprising:
 a first multistage power amplifier including a first plurality of amplifiers of a first class, the first multistage power amplifier configured to amplify a first signal; and   a second multistage power amplifier configured to amplify a second signal that is a phase shifted version of the first signal, the second multistage power amplifier including a second plurality of amplifiers biased within a bias range associated with an amplifier of the first class, at least one of the second plurality of amplifiers biased within a first portion of the bias range and at least one other of the second plurality of amplifiers biased within a second portion of the bias range that differs from the first portion of the bias range such that the second multistage power amplifier mimics a behavior of an amplifier of a second class while each of the second plurality of power amplifiers is biased within the bias range associated with the first class of amplifier.   
     
     
         27 . The Doherty power amplifier of  claim 26  wherein the first signal and the second signal are of equal power and have a phase difference of 90 degrees. 
     
     
         28 . The Doherty power amplifier of  claim 26  further comprising a splitter configured to split an input signal into the first signal and the second signal. 
     
     
         29 . The Doherty power amplifier of  claim 26  further comprising a signal combiner configured to combine an output of the first multistage power amplifier and an output of the second multistage power amplifier to obtain an output signal of the Doherty power amplifier. 
     
     
         30 . The Doherty power amplifier of  claim 26  wherein the first multistage power amplifier is a main amplifier and the second multistage power amplifier is a peaking amplifier. 
     
     
         31 . The Doherty power amplifier of  claim 30  wherein an amplification of the peaking amplifier is less than an amplification of the main amplifier during back off operation. 
     
     
         32 . The Doherty power amplifier of  claim 26  wherein the first multistage power amplifier and the second multistage power amplifier include the same number of power amplifier stages. 
     
     
         33 . The Doherty power amplifier of  claim 26  wherein at least one amplifier of the first multistage power amplifier is biased differently than at least one amplifier of the second multistage power amplifier. 
     
     
         34 . The Doherty power amplifier of  claim 33  wherein a position within the first multistage power amplifier of the at least one amplifier of the first multistage power amplifier corresponds to a position within the second multistage power amplifier of the at least one amplifier of the second multistage power amplifier. 
     
     
         35 . The Doherty power amplifier of  claim 26  wherein at least one other of the second plurality of amplifiers is biased within a third portion of the bias range that differs at least in part from the first portion and the second portion of the bias range. 
     
     
         36 . The Doherty power amplifier of  claim 26  wherein the first plurality of amplifiers are connected in series and the second plurality of amplifiers are connected in series. 
     
     
         37 . The Doherty power amplifier of  claim 26  wherein amplifiers of the first class exhibit a different linearity than amplifiers of the second class. 
     
     
         38 . The Doherty power amplifier of  claim 26  wherein amplifiers of the second class exhibit different power added efficiency than amplifiers of the first class. 
     
     
         39 . The Doherty power amplifier of  claim 26  wherein the amplifier of the first class is a Class-AB amplifier and the amplifier of the second class is a Class-C amplifier.