Slew-rate and efficiency trade-off in slow envelope tracking power amplifiers

This paper presents a study on the trade-off between the envelope´s slew-rate and the drain efficiency when slower envelopes are considered to dynamically supply the power amplifier (PA). This paper discusses a method to limit the slew-rate (and consequently the bandwidth) of the signal´s envelope. Moreover, since the envelope tracking (ET) technique using a slower version of the original envelope introduces nonlinear distortion, slow envelope dependent predistortion has to be also incorporated in the design of ET PAs. Experimental results showed that it is possible to find a compromise between the bandwidth and slew-rate reduction (necessary to cope with the specific envelope amplifier requirements) and the amount of drain efficiency degradation suffered due to the use of a slower version of the original envelope.