Notch FLT

OSC & Freq.

Divider

POR

gm1

gm4

gm2

gm3

Bias

+IN

-IN

Chop1

Chop2

AVDD

AVSS

OUT

AVSS

AVDD

(AVDD)

V+

(AVSS)

V-

10

LPV821

SNOSD36 – AUGUST 2017

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Copyright © 2017, Texas Instruments Incorporated

8 Detailed Description

8.1 Overview

The LPV821 is a zero-drift, nanopower, rail-to-rail input and output operational amplifier. The device operates

from 1.7 V to 3.7 V, is unity-gain stable, and is suitable for a wide range of general-purpose applications. The

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

8.2 Functional Block Diagram

8.3 Feature Description

The LPV821 is unity-gain stable and uses an auto-calibration technique to provide low offset voltage and very

low drift over time and temperature. For lowest offset voltage and precision performance, optimize circuit layout

and mechanical conditions. Avoid temperature gradients that create thermoelectric (Seebeck) effects in the

thermocouple junctions formed from connecting dissimilar conductors. Cancel these thermally-generated

potentials by assuring they are equal on both input terminals. Other layout and design considerations include:

•

Use low thermoelectric-coefficient conditions (avoid dissimilar metals).

•

Thermally isolate components from power supplies or other heat sources.

•

Shield operational amplifier and input circuitry from air currents, such as cooling fans.

Following these guidelines reduces the likelihood of junctions being at different temperatures, which can

cause thermoelectric voltages of 0.1 μV/°C or higher, depending on materials used.

8.3.1 Operating Voltage

The LPV821 operational amplifier operates over a power-supply range of 1.7 V to 3.6V (±0.85 V to ± 1.8 V).

Parameters that vary over supply voltage or temperature are shown in the Typical Characteristics section.

CAUTION

Supply voltages higher than 4 V (absolute maximum) can permanently damage the

device.