An SCR with a first semiconductor region and plural concentric semiconductor regions, each surrounding the first semiconductor region. The SCR also includes, surrounded by at least one concentric semiconductor region in the plurality of concentric semiconductor regions, an electrically non-contacted region of a semiconductor type and positioned to modulate a snapback voltage of the silicon controlled rectifier and an electrically-contacted region of the semiconductor type and positioned to provide a diodic response between the at least one concentric semiconductor region in the plurality of concentric semiconductor regions and the electrically-contacted region.