The GS66504B from GaN Systems is a GaN Power Transistor with Gate Threshold Voltage 1.1 to 2.6 V, Drain Source Voltage 650 V, Drain Source Resistance 100 to 258 milli-ohm, Continous Drain Current 12.5 to 15 A, Pulsed Drain Current 30 A. Tags: Die. More details for GS66504B can be seen below.