The DC path filter 73 and the AC path filter 91 filter the DC voltage V_DC from the MLS DC-to-DC converter 72 and the output of MLS modulator 81, respectively, to thereby generate a power amplifier supply voltage V_PA for the power amplifier 71.

By including a DC path through the DC path filter 73 and a separate AC path through the AC path filter 91, enhanced efficiency of the envelope tracking system 100 can be achieved. For example, low frequency current (including, but not limited to, DC current) can be provided through the DC path filter 73, thereby relaxing size and/or DC resistance constraints of the MLS modulator's switches.

Accordingly, lower switching losses in the AC path can be achieved, thereby enhancing overall system efficiency. In one example, the DC path carries at least 75% of the energy provided by envelope tracking system 100 to the power amplifier 71.

FIG. 3A is a schematic diagram of another embodiment of an envelope tracking system 140 for a power amplifier 101. The envelope tracking system 140 includes an envelope tracking integrated circuit (IC) 102, a DC path filter 103, an AC path filter 104, DAC circuitry 105, an envelope filter 106, first to fourth decoupling capacitors 111-114, respectively, and an inductor 117.

Although one embodiment of an envelope tracking system is shown in FIG. 3A, the teachings herein are applicable to envelope tracking systems implemented in a wide variety of ways. Accordingly, other implementations are possible.