A drive circuit for a half bridge transistor circuit formed of enhancement mode GaN transistors is provided. A shunt diode is connected to the bootstrap capacitor at a node between the bootstrap capacitor and ground, the shunt diode being decoupled from the midpoint node of the half bridge by a shunt resistor. The shunt diode advantageously provides a low voltage drop path to charge the bootstrapcapacitor during the dead-time charging period when both the high side and low side transistors of the half bridge are off.