High Performance, Low Power, Rail-to-Rail
Precision Instrumentation Amplifier
Data Sheet
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
APPLICATIONS
Medical instrumentation
Industrial process controls
Strain gages
Transducer interfaces
Precision data acquisition systems
Channel-isolated systems
Portable instrumentation
CONNECTION DIAGRAM
TOP VIEW
(No t t o Scal e)
11197-001
–IN
1
R
G
2
R
G
3
+IN
4
+V
S
8
V
OUT
7
REF
6
–V
S
5
AD8422
Figure 1. 8-Lead MSOP (RM), 8-Lead SOIC (R)
–140
–130
–120
–110
–100
–90
–80
–70
–60
–50
–40
–30
–20
10
100
1k 5k
AMPLITUDE ( dBc)
FRE Q UE NCY ( Hz )
R
L
=
2kΩ
V
OUT
= ±10V
G = 1000
G = 100
G = 10
G = 1
11197-102
Figure 2. Total Harmonic Distortion vs. Frequency
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.
Ver y 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.
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 on a very
tight error budget.
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 and has typical
performance curves to 125°C. It is available in 8-lead MSOP
and 8-lead SOIC packages.
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