OPA4171-Q1 Datasheet, PDF (17/35 Pages) Texas Instruments – OPAx171-Q1 36-V, Single-Supply, General-Purpose Operational Amplifier

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8 Application and Implementation
OPA171-Q1, OPA2171-Q1, OPA4171-Q1
SBOS556B – JUNE 2011 – REVISED DECEMBER 2014
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
The OPAx171-Q1 operational amplifier provides high overall performance, making it ideal for many general-
purpose applications. The excellent offset drift of only 2 µV/°C provides excellent stability over the entire
temperature range. In addition, the device offers very-good overall performance with high CMRR, PSRR, and
A_OL. As with all amplifiers, applications with noisy or high-impedance power supplies require decoupling
capacitors close to the device pins. In most cases, 0.1-µF capacitors are adequate.
8.1.1 Electrical Overstress
Designers often ask questions about the capability of an op amp 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.
These ESD protection diodes also provide in-circuit, input overdrive protection, as long as the current is limited to
10 mA as stated in the Absolute Maximum Ratings table. Figure 40 shows how a series input resistor can be
added to the driven input to limit the input current. The added resistor contributes thermal noise at the amplifier
input and its value should be kept to a minimum in noise-sensitive applications.
I_OVERLOAD
10mA max
V_IN
5kW
V+
OPA171
V_OUT
Figure 40. Input Current Protection
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 the operational amplifier connects into a circuit, 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 ESD cells and rarely involves the absorption device.
If the ability of the supply to absorb this current is uncertain, external zener diodes may be added to the supply
pins. The zener voltage must be selected such that the diode does not turn on during normal operation.
However, the 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.
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Product Folder Links: OPA171-Q1 OPA2171-Q1 OPA4171-Q1