Microwave class-F InGaP/GaAs HBT power amplifier considering up to 7th-order higher harmonic frequencies

The first realization of a class-F InGaP/GaAs HBT amplifier considering up to 7th-order higher harmonic frequencies, operating at 1.9-GHz band, is described. A total number of open-circuited stubs for higher harmonic frequency treatment is successfully reduced without changing a class-F load circuit condition, using a low-cost and low-loss resin (tan delta = 0.0023) circuit board. In class-F amplifier design at microwave frequency ranges, not only increasing treated orders of higher harmonic frequencies for a class-F load circuit, but also decreasing parasitic capacitances of a transistor is important. Influence of a base-collector capacitance, C-bc, for power added efficiency, PAE, and collector efficiency, eta(c), was investigated by using a two-dimensional device simulator and a harmonic balance simulator. Measured maximum PAE and eta(c) reached 74.2% and 76.6%, respectively, using a fabricated class-F InGaP/GaAs HBT amplifier with collector doping density of 2 x 10(16) cm(-3). In case circuit losses were de-embedded for the experimental results, PAE and eta(c) were estimated as 78.7% and 81.2%, respectively. These are very close to obtainable maximum PAE for the use of the InGaP/GaAs HBT.