OPA227 Datasheet, PDF (16/46 Pages) Burr-Brown (TI) – High Precision, Low Noise OPERATIONAL AMPLIFIERS

OPA227, OPA2227, OPA4227
OPA228, OPA2228, OPA4228
SBOS110B – MAY 1998 – REVISED JUNE 2015
7 Detailed Description
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7.1 Overview
The OPAx22x series operational amplifiers combine low noise and wide bandwidth with high precision to make
them the ideal choice for applications requiring both AC and precision DC performance. The OPAx227 is unity-
gain stable and features high slew rate (2.3 V/µs) and wide bandwidth (8 MHz). The OPAx228 is optimized for
closed-loop gains of 5 or greater, and offers higher speed with a slew rate of 10 V/µs and a bandwidth of 33
MHz.
7.2 Functional Block Diagram
Input Offset
Adjust
(OPA227 and
OPA228 only)
+IN
+
-IN
±
Output
Input Offset
Adjust
(OPA227 and
OPA228 only)
Compensation
7.3 Feature Description
The OPAx22x series are unity-gain stable and free from unexpected output phase reversal, making it easy to use
in a wide range of applications. Applications with noisy or high-impedance power supplies may require
decoupling capacitors close to the device pins. In most cases 0.1-μF capacitors are adequate.
7.3.1 Offset Voltage and Drift
The OPAx22x series have very low offset voltage and drift. To achieve highest DC precision, circuit layout and
mechanical conditions should be optimized. Connections of dissimilar metals can generate thermal potentials at
the operational amplifier inputs, which can degrade the offset voltage and drift. These thermocouple effects can
exceed the inherent drift of the amplifier and ultimately degrade its performance. The thermal potentials can be
made to cancel by assuring that they are equal at both input terminals. In addition:
• Keep thermal mass of the connections made to the two input terminals similar.
• Locate heat sources as far as possible from the critical input circuitry.
• Shield operational amplifier and input circuitry from air currents such as those created by cooling fans.
7.3.2 Operating Voltage
The OPAx22x series of operational amplifiers operate from ±2.5 V to ±18 V supplies with excellent performance.
Unlike most operational amplifiers that are specified at only one supply voltage, the OPA227 series is specified
for real-world applications; a single set of specifications applies over the ±5-V to ±15-V supply range.
Specifications are assured for applications from ±5-V to ±15-V power supplies. Some applications do not require
equal positive and negative output voltage swing. Power supply voltages do not need to be equal. The OPAx22x
series can operate with as little as 5 V between the supplies and with up to 36 V between the supplies. For
example, the positive supply could be set to 25 V with the negative supply at –5 V or vice-versa. In addition, key
parameters are assured over the specified temperature range, –40°C to 85°C. Parameters which vary
significantly with operating voltage or temperature are shown in the Typical Characteristics.
16
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Product Folder Links: OPA227 OPA2227 OPA4227 OPA228 OPA2228 OPA4228