OPA2140AIDR datasheet(20/48 Pages) TI

20 / 48 page

an applied voltage exceeds the operating voltage range of a given pin. Should this condition occur, there is a risk

that some of the internal ESD protection circuits may be biased on, and conduct current. Any such current flow

occurs through steering diode paths and rarely involves the absorption device.

Equivalent Internal ESD Circuitry and Its Relation to a Typical Circuit Application depicts a specific example

where the input voltage, VIN, exceeds the positive supply voltage (+VS) by 500 mV or more. Much of what

happens in the circuit depends on the supply characteristics. If +VS can sink the current, one of the upper input

steering diodes conducts and directs current to +VS. Excessively high current levels can flow with increasingly

higher VIN. As a result, the data sheet specifications recommend that applications limit the input current to 10

mA.

If the supply is not capable of sinking the current, VIN may begin sourcing current to the operational amplifier,

and then take over as the source of positive supply voltage. The danger in this case is that the voltage can rise

to levels that exceed the operational amplifier absolute maximum ratings.

Another common question involves what happens to the amplifier if an input signal is applied to the input while

the power supplies +VS or –VS are at 0 V.

Again, it depends on the supply characteristic while at 0 V, or at a level below the input signal amplitude. If

the supplies appear as high impedance, then the operational amplifier supply current may be supplied by the

input source through the current steering diodes. This state is not a normal bias condition; the amplifier most

likely will not operate normally. If the supplies are low impedance, then the current through the steering diodes

can become quite high. The current level depends on the ability of the input source to deliver current, and any

resistance in the input path.

If there is an uncertainty about the ability of the supply to absorb this current, external Zener diodes may be

added to the supply pins as shown in Equivalent Internal ESD Circuitry and Its Relation to a Typical Circuit

Application. The Zener voltage must be selected such that the diode does not turn on during normal operation.

However, its Zener voltage should be low enough so that the Zener diode conducts if the supply pin begins to

rise above the safe operating supply voltage level.

OPA140, OPA2140, OPA4140

SBOS498E – JULY 2010 – REVISED JULY 2021

www.ti.com

Submit Document Feedback

Product Folder Links: OPA140 OPA2140 OPA4140

OPA2140AIDR Datasheet(PDF) 20 Page - Texas Instruments