Enhancement of power amplifier efficiency through dynamic bias switching

Linear digital modulation techniques in modern communication systems generate carrier signals with relatively high peak-to-average ratio. For linear amplification of such a signal, power amplifier must be operated at excessive back off, thus sacrificing the overall amplifier efficiency. Dynamic bias switching (DBS) can be used to enhance the efficiency of PA and the means to combat the degradation of spectrum regrowth and in-band noise are discussed in this paper. DBS is achieved by partitioning the required supply rail into two or several levels. The supply voltage is switched between the steps, and is adjusted in tune with the signal envelope. This is accomplished by using a pass-transistor (gate) operated as a switch with very low channel resistance. This approach avoids the energy loss associated with continuous tracking (amplification) of the signal envelope reported in the literature.