A 20-W Wide Bandwidth GaN HEMT Power Amplifier for VHF/UHF Applications

In this article, broadband gallium nitride (GaN) high-electron-mobility transistor (HEMT) power amplifier with shunt-feedback and push-pull technique is presented. Shunt-feedback and push-pull realization provide the robust broad bandwidth covering very high frequency and low-frequency ultra high frequency (UHF) bands. The benefit due to the feedback presented in the form of shunt-shunt network on power amplifier module provides the linear and broadband frequency amplification. The push-pull topology provides enhanced efficiency and high power generation along with the cancellation of the second-order distortions and thus helps to compensate for the efficiency degradation from the feedback. These techniques are realized with the help of in-house designed GaN HEMT transistor, which provides high power, good efficiency, and high reliability (bandgap). The prototype was realized in 0.25-μm GaN HEMT, operates from 30 to 520 MHz, and dissipates 650 mA of quiescent current from 28-V supply. The power amplifier delivered a saturated output power of >43 dBm and <1 dB gain flatness with >40% power added efficiency at 20 W output power. The linearity of the amplifier was characterized by the two-tone injection test. The measurement result shows that the third-order intermodulation distortion tones are below $-$35 dBc at 35 dBm output power.