OPA2211-EP Datasheet, PDF (17/32 Pages) Texas Instruments – OPA2211-EP 1.1-nV/√Hz Noise, Low-Power, Precision Operational Amplifier

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8 Application and Implementation
OPA2211-EP
SBOS761 – NOVEMBER 2015
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
8.1.1 Electrical Overstress
Designers often ask questions about the capability of an operational amplifier to withstand electrical overstress.
These questions tend to focus on the device inputs, but may involve the supply voltage pins or even the output
pin. Each of these different pin functions have electrical stress limits determined by the voltage breakdown
characteristics of the particular semiconductor fabrication process and specific circuits connected to the pin.
Additionally, internal electrostatic discharge (ESD) protection is built into these circuits to protect them from
accidental ESD events both before and during product assembly.
It is helpful to have a good understanding of this basic ESD circuitry and its relevance to an electrical overstress
event. Figure 40 illustrates the ESD circuits contained in the OPA2211-EP (indicated by the dashed line area).
The ESD protection circuitry involves several current-steering diodes connected from the input and output pins
and routed back to the internal power-supply lines, where they meet at an absorption device internal to the
operational amplifier. This protection circuitry is intended to remain inactive during normal circuit operation.
An ESD event produces a short duration, high-voltage pulse that is transformed into a short duration, high-
current pulse as it discharges through a semiconductor device. The ESD protection circuits are designed to
provide a current path around the operational amplifier core to prevent it from being damaged. The energy
absorbed by the protection circuitry is then dissipated as heat.
When an ESD voltage develops across two or more of the amplifier device pins, current flows through one or
more of the steering diodes. Depending on the path that the current takes, the absorption device may activate.
The absorption device has a trigger, or threshold voltage, that is above the normal operating voltage of the
OPA2211-EP but below the device breakdown voltage level. Once this threshold is exceeded, the absorption
device quickly activates and clamps the voltage across the supply rails to a safe level.
When the operational amplifier connects into a circuit such as that illustrated in Figure 40, the ESD protection
components are intended to remain inactive and not become involved in the application circuit operation.
However, circumstances may arise where 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.
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