OPA211_15 Datasheet, PDF (21/45 Pages) Texas Instruments – Low Power, Precision Operational Amplifier

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9 Application and Implementation
OPA211, OPA2211
SBOS377H – OCTOBER 2006 – REVISED 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.
9.1 Application Information
The OPA211 and OPA2211 are unity-gain stable, precision operational amplifiers with very-low noise.
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.
9.1.1 Operating Voltage
OPA211 series operational amplifiers operate from ±2.25- to ±18-V supplies while maintaining excellent
performance. The OPA211 series can operate with as little as 4.5 V between the supplies and with up to 36 V
between the supplies. However, some applications do not require equal positive and negative output voltage
swing. With the OPA211 series, power-supply voltages do not need to be equal. For example, the positive supply
could be set to 25 V with the negative supply at –5 V or vice-versa.
The common-mode voltage must be maintained within the specified range. In addition, key parameters are
assured over the specified temperature range, T_A = –40°C to +125°C. Parameters that vary significantly with
operating voltage or temperature are shown in the Typical Characteristics.
9.1.2 Input Protection
The input terminals of the OPA211 are protected from excessive differential voltage with back-to-back diodes, as
shown in Figure 44. In most circuit applications, the input protection circuitry has no consequence. However, in
low-gain or G = 1 circuits, fast ramping input signals can forward bias these diodes because the output of the
amplifier cannot respond rapidly enough to the input ramp. This effect is shown in Figure 30 of the Typical
Characteristics. If the input signal is fast enough to create this forward bias condition, the input signal current
must be limited to 10 mA or less. If the input signal current is not inherently limited, an input series resistor can
be used to limit the signal input current. This input series resistor degrades the low-noise performance of the
OPA211, and is discussed in the Noise Performance section of this data sheet. Figure 44 shows an example
implementing a current-limiting feedback resistor.
R_F
-
Input
R_I
+
OPA211
Output
Figure 44. Pulsed Operation
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Product Folder Links: OPA211 OPA2211
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