An output stage of a switching DC-DC converter includes a pair of transistors and a bias transistor connected between the transistors. A voltage regulator generates a bias voltage to bias a control terminal of the bias transistor with a fixed bias voltage. The voltage regulator is operable in a full-power mode and a low-power mode. The voltage regulator consumes larger current in the full-power mode than in the low-power mode. At low load currents, the voltage regulator is operated in the low-power mode when both the transistors in the pair of transistors are off, and in the full-power mode otherwise.