부산대학교 도서관

This letter presents an inverse class-F power amplifier (PA) where the second-harmonic voltage produced by the nonlinear gate–source capacitor ( $C_{\text {GS}}$ ) of the gallium nitride (GaN) HEMT transistor improves the PAE and output power. The design is based on multiharmonic recursive source-pull (SP) and load-pull (LP) simulations to determine the optimum design space. With proper impedance terminations at $f_{{0}}$ and ${2}f_{{0}}$ , the second-harmonic input voltage improves the PAE by about 10%. An ${X}$ -band proof-of-concept PA is implemented in a 250-nm GaN technology with a $f_{\text {max}}$ of 50 GHz. At 9.5-GHz center frequency, 17.8 W peak output power and 43% power added efficiency are achieved for pulsed-mode operation with a pulse repetition frequency of 10 kHz and a duty cycle of 10%. The designed three-stage PA consumes 7.72 mm2 die area and dissipates about 39 W dc power at saturation.