The SP725 is an array of SCR/Diode bipolar structures for ESD and overvoltage protection of sensitive input circuits. The SP725 has 2 protection SCR/Diode device structures per input. There are a total of 4 available inputs that can be used to protect up to 4 external signal or bus lines. Over-voltage protection is from the IN (Pins 1 - 4) to V+ or V-. The SCR structures are designed for fast triggering at a threshold of one +VBE diode threshold above V+ (Pin 5,6) or one –VBE diode threshold below V- (Pin 7,8). From an IN input, a clamp to V+ is activated if a transient pulse causes the input to be increased to a voltage level greater than one VBE above V+. A similar clamp to V- is activated if a negative pulse, one VBE less than V-, is applied to an IN input.