A DC-DC buck converter comprises a high-side power FET having a current path connected in series between an input terminal and an inductor connected to an output terminal supplying an output current to a load. The converter further comprises a low-side power FET having a current path connected between a reference terminal and an interconnection node of the high-side power FET with the inductor. The converter has a pulse width modulation controller receiving a feedback signal from the output terminal and providing pulse width modulated signals, and a gate driver circuit that receives the pulse width modulated signals from the pulse width modulation controller and applies pulse width modulated drive signals to the gates of the power FETs. The gate driver circuit supplies the drive signals to the gates of the power FETs at a variable voltage level adjusted in response to at least the output current, minimizing the power dissipation of the gate driver circuit.