We present a design example to multiply output power from high-voltage GaN HEMTs in converter applications. A design process starting with a robust unit-cell design, employing equal-length transmission-line gate drives and short drain terminations successfully doubled and quadrupled output power with little efficiency degradation. A 4-kW 220V:400V boost converter at 100-kHz was demonstrated using 4 GaN HEMTs achieving >99% efficiency from 15% to 90% load.