OPA2211-EP_16 Datasheet, PDF (14/32 Pages) Texas Instruments – Low-Power, Precision Operational Amplifier

OPA2211-EP
SBOS761 – NOVEMBER 2015
7 Detailed Description
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7.1 Overview
The OPA2211-EP is a unity-gain stable, precision operational amplifier 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. Functional Block Diagram shows a simplified schematic of the OPA2211-EP.
This die uses a SiGe bipolar process and contains 180 transistors.
7.2 Functional Block Diagram
V+
Pre-Output Driver
IN-
IN+
OUT
V-
7.3 Feature Description
7.3.1 Input Protection
The input terminals of the OPA2211-EPFigure 38 are protected from excessive differential voltage with back-to-
back diodes, as shown in . 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 illustrated in Figure 29 in
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 OPA2211-EP, and is discussed in Noise Performance. Figure 38 shows an example
implementing a current-limiting feedback resistor.
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