Low Drift, Low Power
Instrumentation Amplifier
a
AD621
CONNECTION DIAGRAM
8-Pin Plastic Mini-DIP (N), Cerdip (Q)
and SOIC (R) Packages
FEATURES
EASY TO USE
Pin-Strappable Gains of 10 & 100
All Errors Specified for Total System Performance
Higher Performance than Discrete In-Amp Designs
Available in 8-Pin DIP and SOIC
Low Power, 1.3 mA max Supply Current
Wide Power Supply Range (؎2.3 V to ؎18 V)
8
G=10/100
1
2
3
4
G=10/100
–IN
AD621
7
6
5
+V
S
OUTPUT
REF
+IN
EXCELLENT DC PERFORMANCE
0.15% max, Total Gain Error
؎5 ppm/؇C, Total Gain Drift
–V
S
TOP VIEW
125 V max, Total Offset Voltage
1.0 V/؇C max, Offset Voltage Drift
pin strapping. The AD621 is fully specified as a total system,
therefore, simplifying the design process.
LOW NOISE
9 nV/√Hz, @ 1 kHz, Input Voltage Noise
0.28 V p-p Noise (0.1 Hz to 10 Hz}
For portable or remote applications, where power dissipation,
size and weight are critical, the AD621 features a very low sup-
ply current of 1.3 mA max and is packaged in a compact 8-pin
SOIC, 8-pin plastic DIP or 8-pin cerdip. The AD621 also
excels in applications requiring high total accuracy, such as pre-
cision data acquisition systems used in weigh scales and trans-
ducer interface circuits. Low maximum error specifications
including nonlinearity of 10 ppm, gain drift of 5 ppm/°C, 50 µV
offset voltage and 0.6 µV/°C offset drift (“B” grade), make pos-
sible total system performance at a lower cost than has been pre-
viously achieved with discrete designs or with other monolithic
instrumentation amplifiers.
EXCELLENT AC SPECIFICATIONS
800 kHz Bandwidth (G = 10}, 200 kHz (G = 100}
12 s Settling Time to 0.01%
APPLICATIONS
Weigh Scales
Transducer Interface & Data Acquisition Systems
Industrial Process Controls
Battery Powered and Portable Equipment
PRODUCT DESCRIPTION
The AD621 is an easy to use, low cost, low power, high accu-
racy instrumentation amplifier which is ideally suited for a wide
range of applications. Its unique combination of high perfor-
mance, small size and low power, outperforms discrete in amp
implementations. High functionality, low gain errors and low
gain drift errors are achieved by the use of internal gain setting
resistors. Fixed gains of 10 and 100 can be easily set via external
When operating from high source impedances, as in ECG and
blood pressure monitors, the AD621 features the ideal combina-
tion of low noise and low input bias currents. Voltage noise is
specified as 9 nV/√Hz at 1 kHz and 0.28 µV p-p from 0.1 Hz to
10 Hz. Input current noise is also extremely low at 0.1 pA/√Hz.
The AD621 outperforms FET input devices with an input bias
current specification of 1.5 nA max over the full industrial tem-
perature range.
30,000
10,000
25,000
3 - OP AMP
IN-AMPS
TYPICAL STANDARD
1,000
BIPOLAR INPUT
20,000
(3 OP 07'S)
IN-AMP
15,000
100
AD621A
10,000
10
AD621 SUPERßETA
5,000
0
BIPOLAR INPUT
IN-AMP
1
10
5
15
20
SUPPLY CURRENT – mA
0.1
10k
100k
SOURCE RESISTANCE – Ω
10M
100M
1k
1M
Three Op Amp IA Designs vs. AD621
Total Voltage Noise vs. Source Resistance
REV. A
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
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Tel: 617/329-4700
Fax: 617/326-8703