Protection circuit for input=output circuit

摘要

The circuit includes a diode, and an npn transistor. The diode is coupled to an inner circuit contact point in the forward direction. The npn-transistor has its emitter coupled to the inner circuit contact point, its collector coupled to a supply voltage. The transistor also has a floating base. The e.g. input/output circuit forms an inner circuit protected from a voltage lower than a reference voltage, or from a voltage higher than the operational voltage. This voltage is applied to the contact point of the inner circuit.