The paper discusses the bandwidth extension of a second-harmonic tuned GaN Doherty power amplifier: the adopted strategy relies on output wideband compensation stages and input broadband matching. The single-band (3.5 GHz) and the wide-band (3-3.6 GHz) power amplifiers are compared in terms of building blocks design strategy. The performances, experimentally characterized in single- and two-tone conditions, are close to the state-of-the art for these applications, and confirm the validity of the bandwidth extension approach. In fact, output power of more than 43dBm and 6dB back-off efficiency of around 40% are maintained by the bandwidth extension strategy, as well as intermodulation ratio values. Furthermore, digital baseband predistortion is successfully applied to both stages.