Precision Instrumentation Amplifier
AD8221
Rev. C
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FEATURES
Easy to use
Available in space-saving MSOP
Gain set with 1 external resistor (gain range 1 to 1000)
Wide power supply range: ±2.3 V to ±18 V
Temperature range for specified performance:
−40°C to +85°C
Operational up to 125°C
1
Excellent AC specifications
80 dB minimum CMRR to 10 kHz (G = 1)
825 kHz, –3 dB bandwidth (G = 1)
2 V/µs slew rate
Low noise
8 nV/√Hz, @ 1 kHz, maximum input voltage noise
0.25 µV p-p input noise (0.1 Hz to 10 Hz)
High accuracy dc performance (AD8221BR)
90 dB minimum CMRR (G = 1)
25 µV maximum input offset voltage
0.3 µV/°C maximum input offset drift
0.4 nA maximum input bias current
APPLICATIONS
Weigh scales
Industrial process controls
Bridge amplifiers
Precision data acquisition systems
Medical instrumentation
Strain gages
Transducer interfaces
GENERAL DESCRIPTION
The AD8221 is a gain programmable, high performance
instrumentation amplifier that delivers the industry’s highest
CMRR over frequency in its class. The CMRR of instrumentation
amplifiers on the market today falls off at 200 Hz. In contrast,
the AD8221 maintains a minimum CMRR of 80 dB to 10 kHz
for all grades at G = 1. High CMRR over frequency allows the
AD8221 to reject wideband interference and line harmonics,
greatly simplifying filter requirements. Possible applications
include precision data acquisition, biomedical analysis, and
aerospace instrumentation.
CONNECTION DIAGRAM
8
7
6
5
1
2
3
4
–IN
R
G
R
G
+V
S
V
OUT
REF
–V
S
+IN
TOP VIEW
AD8221
0
3
1
4
9
-0
0
1
Figure 1.
40
50
60
70
80
90
C
MR
R
(d
B
)
100
110
120
FREQUENCY (Hz)
100
10
1k
10k
100k
0
3
1
4
9
-0
0
2
AD8221
COMPETITOR 1
COMPETITOR 2
Figure 2. Typical CMRR vs. Frequency for G = 1
Low voltage offset, low offset drift, low gain drift, high gain
accuracy, and high CMRR make this part an excellent choice
in applications that demand the best dc performance possible,
such as bridge signal conditioning.
Programmable gain affords the user design flexibility. A single
resistor sets the gain from 1 to 1000. The AD8221 operates on
both single and dual supplies and is well suited for applications
where ±10 V input voltages are encountered.
The AD8221 is available in a low cost 8-lead SOIC and 8-lead
MSOP, both of which offer the industry’s best performance. The
MSOP requires half the board space of the SOIC, making it ideal
for multichannel or space-constrained applications.
Performance is specified over the entire industrial temperature
range of −40°C to +85°C for all grades. Furthermore, the AD8221
is operational from −40°C to +125°C
1
.
1
See Typical Performance Characteristics for expected operation from
85°C to 125°C.
