The OPA3S328 incorporates internal electrostatic discharge (ESD) protection circuits on all pins. In the case of input and output pins, this protection primarily consists of current-steering diodes connected between the input and power-supply pins. These ESD protection diodes also provide in-circuit input overdrive protection, provided that the current is limited to 10 mA. Many input signals are inherently current-limited to less than 10 mA; therefore, a limiting resistor is not required. Figure 7-1 shows how a series input resistor (R_S) can be added to the driven input to limit the input current. The added resistor contributes thermal noise at the amplifier input; therefore, keep this value to a minimum in noise-sensitive applications.

Figure 7-1 Input Current Protection