Driver circuitry for switching systems comprising enhancement mode (E-Mode) GaN power transistors with low threshold voltage is disclosed. An E-Mode high electron mobility transistor (HEMT) D3 has a monolithically integrated GaN driver, comprising smaller E-Mode GaN HEMTs D1 and D2, and a discrete dual-voltage pre-driver. In operation, D1 provides the gate drive voltage to the gate of the GaN switch D3, and D2 clamps the gate of the GaN switch D3 to the source, via an internal source-sense connection closely coupling the source of D3 and the source of D2. An additional source-sense connection is provided for the pre-driver. Boosting the drive voltage to the gate of D1 produces firm and rapid pull-up of D1 and D3 for improved switching performance at higher switching speeds. High current handling components of the driver circuitry are integrated with the GaN switch and closely coupled to reduce inductance, while the discrete pre-driver can be thermally separated from the GaN chip.