The inputs are protected with internal diodes connected to the power-supply rails. These diodes clamp the applied signal to prevent the signal from exceeding the power supplies by more than approximately 0.7 V. If the signal-source voltage can exceed the power supplies, the source current should be limited to less than 10 mA. This limiting can generally be done with a series resistor. Some signal sources are inherently current-limited, and do not require limiting resistors.