Supply Rails

Document created by analog-archivist Employee on Feb 23, 2016
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What happens if the input is driven beyond the supply rails?

 

The input stages have internal clamped diodes that are connected from the
inputs to each supply rail. These diodes protect the input transistors in the
event of electrostatic discharge and are reverse biased during normal
operation. This protection scheme allows voltages as high as approximately
300mV beyond the rails to be applied at the input terminals without causing
permanent damage. However, when either of the input exceeds one of the supply
rails by more than 300mV, the diodes become forward biased and large amounts of
current begin to flow through them. In this case, insert a resistor in series
with each input to limit the input current to 10mA maximum. Without current
limiting, the excessive fault current will cause permanent damage to the
device.

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