Abstract
<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A novel pulsed class-B load–pull measurement system is developed to characterize GaN HEMTs targeting the design of high-efficiency class-B or class-C power amplifiers operating under a pulsed-bias and pulsed-RF (pulsed-<emphasis emphasistype="boldital">IV</emphasis>/RF) condition. Based on a large-signal network analyzer, the test system uses an active load–pull method to provide stable open-loop pulsed-RF loads into the drain at <formula formulatype="inline"> <tex Notation="TeX">$\omega_0$</tex></formula> and <formula formulatype="inline"> <tex Notation="TeX">$2\omega_0$</tex></formula> while bypassing slow-memory effects. The load–pull measurement data obtained from AlGaN/GaN HEMTs under the class-B operation reveal that there exist optimal loads for pulsed-<emphasis emphasistype="boldital">IV</emphasis>/RF condition, which differ from the ones found for a dc–<emphasis emphasistype="boldital">IV</emphasis> and continuous wave condition. This is due to the avoidance of slow-memory effects in the pulsed-<emphasis emphasistype="boldital">IV</emphasis>/RF load–pull measurements, which are known to degrade the device RF performance: a 2-dB increase in output power is obtained for a GaN HEMT on sapphire. The optimized pulsed-RF active load for a GaN HEMT on SiC demonstrates a power-added efficiency of 82% with 17.8-dBm output power under quasi class-B pulsed operation at 2 GHz. </para>
Published Version
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