Continuous harmonically tuned Class-B power amplifier: A closed form equation design approach

This paper presents a set of closed form equations for the calculation of the impedances for the continuous harmonically tuned (HT) Class-B power amplifier (PA). These equations have been derived by assuming a “quartic” drain current rather than the usually assumed half-wave rectified sinusoidal wave current. The resulting impedances were verified in simulations using a proven, large-signal GaN transistor model at three frequencies (900MHz, 2.1GHz and 3.5GHz). Moreover, a PA was built and measured at 2.1GHz, based on a 10W GaN HEMT transistor, achieving a power added efficiency (PAE) of 72.8% at maximum output power confirming the proposed design approach.