The dual diode configuration is great for most op amp protection, but this is not preferred if the inputs have higher voltages than the supplies. This type of protection has issues if an input signal is applied to an amplifier before the amplifier is powered on. Some applications can turn off power on equipment, but still apply an input signal. Without additional protection, the dual diode configuration does not protect well against these input signals. This issue is explained later in the Electrical Overstress section of this document.

Open drain output is another scenario where dual diode configuration is not a good option. An open drain output is when the output of the device is connected to the drain of a transistor. In this setup, the device can only sink current. In cases of an open drain output, the traditional dual diodes are not placed on the output. Otherwise, the voltage clamp at the supply level, and the device is not be able to function as intended. Examples of this include timers, some comparators, and various differential amplifiers. Difference amplifiers often have an input signal that is higher than the supply voltage, making alternative methods of protection required against ESD.