A switching transistor (5) has its collector connected to a common junction (J) with a load (6), typically an ignition coil (8). A first driver transistor (11) connected through the base-emitter path of a second driver transistor (12) to control the conduction state of the switching transistor. A signal source (20, 21) alternatingly, causing the driver transistor to be blocked or conductive. To decrease the power requirements on the driver transistor, the driver transistor has its collector connected to the common junction (J) the voltage at line (13) of the driver and of the junction being arranged that the voltage at the junction (J) is less than the voltage at the base of the driver transistor when the switching transistor (5) is in fully saturated conductive condition, re-combination of charge carriers on the base of the switching transistor maintaining the switching transistor conductive until the charge carriers are exhausted, which causes a slight rise in voltage at the junction (J), but then causes increased conduction of the driver transistor due to the then overriding control from the driver transistor (11). The charge carriers, thereby, removing part of the load on the driver transistor. To insure rapid turn-off of the switching transistor (5), a control transistor (19) has its collector-emitter path connected across the base-emitter path of the switching transistor and, when rendered conductive, will cause the switching transistor to rapidly change to the blocked state.