OPA4188 Datasheet, PDF (17/35 Pages) Texas Instruments – Zero-Drift Operational Amplifiers

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8 Detailed Description
OPA4188
SBOS641C – JUNE 2012 – REVISED NOVEMBER 2015
8.1 Overview
The OPA4188 operational amplifier combines precision offset and drift with excellent overall performance,
making the device ideal for many precision applications. The precision offset drift of only 0.085 μV per degree
Celsius provides stability over the entire temperature range. In addition, the device offers excellent overall
performance with high CMRR, PSRR, and AOL. 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. The OPA4188 is developed using TI's proprietary auto-zero architecture shown in Functional Block
Diagram. The internal synchronous notch filter removes switching noise from the CHOP1 and CHOP2 stages,
resulting in a low noise density of 8.8 nV/Hz, low input offset voltage maximum of only 25 µV. Input offset drift
maximum of only 0.085 µV/°C allows for calibration free system design.
8.2 Functional Block Diagram
C2
CHOP1
GM1
CHOP2
Notch
Filter
GM2
+IN
-IN
GM3
OUT
GM_FF
C1
8.3 Feature Description
8.3.1 Phase-Reversal Protection
The OPA4188 has an internal phase-reversal protection. Many op amps exhibit a phase reversal when the input
is driven beyond its linear common-mode range. This condition is most often encountered in noninverting circuits
when the input is driven beyond the specified common-mode voltage range, causing the output to reverse into
the opposite rail. The OPA4188 input prevents phase reversal with excessive common-mode voltage. Instead,
the output limits into the appropriate rail. This performance is shown in Figure 39.
+18 V
Device
-18 V
37 VPP
Sine Wave
(±18.5 V)
V_IN
V_OUT
Time (100 ms/div)
Figure 39. No Phase Reversal
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