Abstract
A hybrid supply modulator (HSM) is proposed for the envelope-tracking power amplifier (ET-PA) to improve its power- added efficiency (PAE). The proposed HSM consists of a linear amplifier (LA) and a switching amplifier (SA). The LA adopts a current-recycling OTA (CROTA) followed by an IQ-controlled class- AB output stage. The CROTA enhances gain and slew rate of the LA first stage. In the class-AB output stage, the quiescent current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</sub> ) is regulated to reduce its sensitivity to process and supply variations. The SA employs a zero-peaked hysteresis comparator for switching control, which reduces the time delay of the SA control loop, and leads to better power efficiency. Measurement results shows that the HSM reaches 75.2% efficiency at 29.3-dBm output power. When tested with a commercial PA, the PAE improves by 17.3% at 22-dBm RF output power with 34.9-dB power gain.
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