An integrated circuit includes a gate driver circuit that controls high side and low side transistors to operate in buck or boost mode. In buck operating mode, after switching off the low side transistor, the gate driver circuit controls the high side transistor in a constant current mode. After the low side transistor is disabled and no longer conducts current, then the gate driver circuit controls the high side transistor to operate in full-enhancement mode. In boost operating mode, after switching off the high side transistor, the gate driver circuit controls the low side transistor in a constant current mode. After the high side transistor is disabled, then the gate driver circuit controls the low side switching transistor to operate in full-enhancement mode. In both buck and boost operation, the gate driver circuit operates without dead time in which both the high side and low side transistors are off.