Electronic switch

An electronic switch with two transistors connected in a Darlington configuration. A first of the two transistors has collector-emitter terminals connected between input and output terminals. A regulator monitors the output voltage and controls the duty cycle of a switch providing base drive current to the second transistor of the Darlington pair. Current from the switch is also provided to a second switch which is connected to the base of the first transistor. The second switch is a comparator which monitors the voltage of the input terminal as compared to a reference. When the difference between the voltages at the input and output terminals is low, the second switch is closed so that the first transistor is driven by the current through the first switch directly. When the difference between the input voltage and output voltage is high, the second switch opens so that the two transistors are operative as a Darlington pair. The electronic switch in the preferred embodiment is employed in a switching regulator.