An electronic delay circuit (10) for use in a detonator (100) has a switching circuit (20) and a timer circuit (22). Switching circuit (20) controls the flow of a stored charge of electrical energy from a storage capacitor (12) to a bridge initiation element such as a semiconductor bridge (18) or a tungsten bridge. The timing of the release of this energy is controlled by timer circuit (22). Switching circuit (20) is an integrated, dielectrically isolated, bipolar CMOS (DI BiCMOS) circuit, whereas timer circuit (22) is a conventional CMOS circuit. The use of a DI BiCMOS switching circuit allows for greater efficiency of energy transfer from the storage capacitor (12) to the semiconductor bridge (18) than has previously been attained.