Most of the time, instrumentation amplifiers cannot tolerate input voltages beyond their supplies. Most instrumentation amplifiers contain ESD diodes at the supply inputs. If a voltage goes beyond the supplies, one of these ESD diodes can turn on. If the current is not limited, the part will be damaged by the excessive current flow. The In Amp is typically the first IC in the signal chain, connected to the outside world through leads. Accidents can happen – for example being connected to the wrong sensor, or even the right sensor when the In Amp’s power is off. In Amp circuits be designed to handle these fault conditions.