In the substrate (23) of an integrated circuit, around a pad area, a first region (24) of the first conductivity type having a high doping level in turn formed in a second region (25) of the second conductivity type and, beyond the first region with respect to the pad, a third region (26) of the second...http://www.google.de/patents/US4897757?utm_source=gb-gplus-sharePatent US4897757 - Protection structure for an integrated circuit
