High Performance, Low Power, Rail-to-Rail

Precision Instrumentation Amplifier

Data Sheet

AD8422

Rev. B

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FEATURES

Low power: 330 µA maximum quiescent current

Rail-to-rail output

Low noise and distortion

8 nV/√Hz maximum input voltage noise at 1 kHz

0.15 µV p-p RTI noise (G = 100)

0.5 ppm nonlinearity with 2 kΩ load (G = 1)

Excellent ac specifications

80 dB minimum CMRR at 10 kHz (G = 1)

2.2 MHz bandwidth (G = 1)

High precision dc performance (AD8422BRZ)

150 dB minimum CMRR (G = 1000)

0.04% maximum gain error (G = 1000)

0.3 µV/°C maximum input offset drift

0.5 nA maximum input bias current

Wide supply range

4.6 V to 36 V single supply

±2.3 V to ±18 V dual supply

Input overvoltage protection: 40 V from opposite supply

Gain range: 1 to 1000

Available in 8-lead LFCSP, 8-lead MSOP, and 8-lead SOIC_N

APPLICATIONS

Medical instrumentation

Industrial process controls

Strain gages

Transducer interfaces

Precision data acquisition systems

Channel-isolated systems

Portable instrumentation

GENERAL DESCRIPTION

The AD8422 is a high precision, low power, low noise, rail-to-rail

instrumentation amplifier that delivers the best performance

per unit microampere in the industry. The AD8422 processes

signals with ultralow distortion performance that is load

independent over its full output range.

The AD8422 is the third generation development of the industry-

standard AD620. The AD8422 employs new process technologies

and design techniques to achieve higher dynamic range and

lower errors than its predecessors, while consuming less than

one-third of the power. The AD8422 uses the high performance

pinout introduced by the AD8221.

Very low bias current makes the AD8422 error free with high

source impedance, allowing multiple sensors to be multiplexed

to the inputs. Low voltage noise and low current noise make the

AD8422 an ideal choice for measuring a Wheatstone bridge.

TYPICAL APPLICATION DIAGRAM

+5V

+5V

+5V

REF

+24V

+IN

10.7kΩ

24.9kΩ

1

ZERO ADJUST

–IN

±15mV

V = 0.5V TO 2.5V

G = 66.8V/V

AD8422

ADA4096-2

Figure 1. Bridge Amplifier with Output Zero Adjust

The wide input range and rail-to-rail output of the AD8422

bring all of the benefits of a high performance in-amp to single-

supply applications. Whether using high or low supply voltages,

the power savings make the AD8422 an excellent choice for

high channel count or power sensitive applications.

The AD8422 uses robust input protection that ensures reliability

without sacrificing noise performance. The AD8422 has high

ESD immunity, and the inputs are protected from continuous

voltages up to 40 V from the opposite supply rail.

A single resistor sets the gain from 1 to 1000. The reference pin

can be used to apply a precise offset to the output voltage.

The AD8422 is specified from −40°C to +85°C for the 8-lead

MSOP and the 8-lead SOIC_N and from −40°C to +125°C for

the 8-lead LFCSP.

–140

–130

–120

–110

–100

–90

–80

–70

–60

–50

–40

–30

–20

10

100

1k

5k

FREQUENCY (Hz)

G = 1000

G = 100

G = 10

G = 1

Figure 2. Total Harmonic Distortion vs. Frequency