This letter experimentally investigates and discusses the effects of output harmonic termination on power added efficiency (PAE) and output power of an AlGaN/GaN high electron mobility transistor (HEMT) power amplifier (PA). The AlGaN/GaN HEMT PA with gate periphery of 1 mm was built and tested at L-band. Large-signal measurements and comparisons of the PAE and output power were carried out at different dc bias conditions from 50% of saturated drain current (Idss) to 1% of Idss for the PA with and without output harmonic termination. For class-AB operation at 25% of Idss, an increase of about 10% in peak PAE and 1 dBm in output power were observed in saturated output power range. Improvements of up to 9% in PAE and 1.2 dBm in output power were achieved over the measured dc bias conditions provided the output harmonics are properly terminated.
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