Two-Stage GaN HEMT Amplifier With Gate–Source Voltage Shaping for Efficiency Versus Bandwidth Enhancements

Abstract

In this paper a two-stage 2-GHz GaN HEMT amplifier with 15-W output power, 28-dB power gain, and 70% poweradded efficiency (PAE) is presented.The power stage is designed to operate under class F conditions. The driver stage operates under class F 1 conditions and feeds the power stage with both fundamental and second harmonic components. The inter stage matching is designed to target a quasi-half sine voltage shape at the intrinsic gate port of the power stage. The goal is to reduce aperture angle of the power stage and get PAE improvements over a wide frequency bandwidth.In addition to the amplifier design description, this paper reports original time-domain waveform measurements at internal nodes of the designed two-stage power amplifier using calibrated high-impedance probes and large signal network analyzer. Furthermore, waveform measurements recorded at different frequencies show that aperture angle remains reduced over large frequency bandwidth. In this study, a PAE greater than 60% is reached over 20% frequency bandwidth. Index Terms-Aperture angle, classes F and F 1 , GaN power amplifier (PA), power-added efficiency (PAE), waveform measurements.

A 18‐23 GHz power amplifier design using approximate optimal impedance region approach for satellite downlink

“…In order to further improve the overall efficiency of the MMIC, the second stage device is also operated in the near saturation region. At the same time, according to References 25‐27, for power stage devices under harmonic modulation, changing the voltage waveform of the input signal can improve the efficiency and output power of devices effectively. The effect is most obvious when the voltage waveform is a half sine or square wave.…”

Analysis of the third harmonic for class-F power amplifiers with an I – V knee effect

“…As known to all, the drain current of the ideal class-B PA can be written as I d,ideal = max((I q + I max cos(wt)), 0), (7) where I q is the normalized quiescent drain current, and I max is the normalized maximum radio frequency (RF) current. Since the drain voltage is positive and the input voltage is less than a threshold value, the drain current is also above 0.…”

“…A 70% power added efficiency (PAE) class-F PA was realized through tuning the input waveform. [7] In Ref. [8], the author made a class-F and class-F −1 PA by shorting the second harmonic, while the third harmonic opening and second harmonic opening while third harmonic shorting achieved 76% and 82% PAE, respectively.…”

A high‐efficiency gan power amplifier with harmonic control based on Si‐IPDS

“…A Class‐F power amplifier with control of the gate‐source voltage waveform shape achieves significantly higher efficiency than conventional Class‐F amplifier. A GaN power amplifier showing a 25‐point PAE improvement by controlling the gate‐source voltage waveform shape has also been reported . The Class‐F output matching network, using lumped elements including spiral inductors and interdigital capacitors, provides smaller dimensions than a matching network using transmission lines.…”