Patent ID: 7570467

Claim:
An electrostatic protection circuit being an integrated circuit on a semiconductor substrate and including a first power supply terminal having a predetermined potential, a second power supply terminal having a lower potential than the predetermined potential, and an input/output terminal for a signal, the electrostatic protection circuit comprising: first and second diodes having respective cathode electrodes thereof connected in series at a first common connection point between the first power supply terminal and the input/output terminal; third and fourth diodes having respective anode electrodes thereof connected in series at a second common connection point between the second power supply terminal and the input/output terminal; a first discharge element, connected between the first and second common connection points, for discharging excessive static electricity; and a second discharge element, connected between the first and second power supply terminals, for discharging excessive static electricity, wherein both of the first and second common connection points are internal intermediate nodes to which potential is internally supplied directly in the electrostatic protection circuit and is not externally supplied directly from outside of the electrostatic protection circuit, and wherein the internal intermediate nodes are not directly electrically connected with an internal circuit which the electrostatic protection circuit protects.