Time(100 s/div)

m

+18V

-18V

37V

PP

SineWave

( 18.5V)

±

Device

V

IN

V

OUT

GM1

+IN

-IN

CHOP1

CHOP2

Notch

Filter

GM_FF

GM2

GM3

C2

C1

OUT

17

OPA4188

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SBOS641D – JUNE 2012 – REVISED SEPTEMBER 2016

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8 Detailed Description

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 device 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

8.3 Feature Description

8.3.1 Phase-Reversal Protection

The OPA4188 device 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.

Figure 39. No Phase Reversal