GM1

+IN

-IN

CHOP1

CHOP2

Notch

Filter

GM_FF

GM2

GM3

C2

C1

OUT

V+

V-

Copyright © 2016, Texas Instruments Incorporated

15

OPA187, OPA2187, OPA4187

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SBOS807 – DECEMBER 2016

Product Folder Links: OPA187 OPA2187 OPA4187

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Copyright © 2016, Texas Instruments Incorporated

7 Detailed Description

7.1 Overview

The OPAx187 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 0.005 µV/°C provides

stability over the entire temperature range. In addition, this device offers excellent overall performance with high

decoupling capacitors close to the device pins. In most cases, 0.1-µF capacitors are adequate.

The OPAx187 device is part of a family of zero-drift, low-power, rail-to-rail output operational amplifiers. These

devices operate from 4.5 V to 36 V, are unity-gain stable, and are suitable for a wide range of general-purpose

applications. The zero-drift architecture provides ultra-low input offset voltage and near-zero input offset voltage

drift over temperature and time. This choice of architecture also offers outstanding ac performance, such as ultra-

low broadband noise and zero flicker noise.

7.2 Functional Block Diagram

Figure 36 shows a representation of the proprietary OPAx187 architecture. Functional blocks CHOP1 and

CHOP2 operate such that the non-idealities of GM1 are cancelled while the input signal is left in-phase. The

integrated notch filter of the OPAx187 family suppresses most of the auto-zero amplifier carrier.

Figure 36. Functional Block Diagram