CONNECTION DIAGRAM
8-Lead Plastic Mini-DIP (N), Cerdip (Q)
and SOIC (R) Packages
TOP VIEW
(Not to Scale)
8
7
6
5
1
2
3
4
G = 10/100
–IN
+IN
G = 10/100
+V
S
OUTPUT
REF–V
S
AD621
REV.B
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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.
a
Low Drift, Low Power
Instrumentation Amplifier
AD621
FEATURES
EASY TO USE
Pin-Strappable Gains of 10 and 100
All Errors Specified for Total System Performance
Higher Performance than Discrete In Amp Designs
Available in 8-Lead DIP and SOIC
Low Power, 1.3 mA Max Supply Current
Wide Power Supply Range (H115502.3 V to H1155018 V)
EXCELLENT DC PERFORMANCE
0.15% Max, Total Gain Error
H115505 ppm/H11543C, Total Gain Drift
125 H9262V Max, Total Offset Voltage
1.0 H9262V/H11543C Max, Offset Voltage Drift
LOW NOISE
9 nV/√Hz, @ 1 kHz, Input Voltage Noise
0.28 H9262V p-p Noise (0.1 Hz to 10 Hz)
EXCELLENT AC SPECIFICATIONS
800 kHz Bandwidth (G = 10), 200 kHz (G = 100)
12 H9262s Settling Time to 0.01%
APPLICATIONS
Weigh Scales
Transducer Interface and 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 that 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
SUPPLY CURRENT – mA
30,000
25,000
0
0205
T
O
T
A
L ERR
OR,
ppm OF FULL SCALE
10 15
20,000
15,000
10,000
5,000
AD621A
3 OP AMP
IN AMP
(3 OP 07S)
Figure 1. Three Op Amp IA Designs vs. AD621
gain drift errors are achieved by the use of internal gain setting
resistors. Fixed gains of 10 and 100 can easily be set via external
pin strapping. The AD621 is fully specified as a total system,
therefore, simplifying the design process.
For portable or remote applications, where power dissipation,
size, and weight are critical, the AD621 features a very low
supply current of 1.3 mA max and is packaged in a compact
8-lead SOIC, 8-lead plastic DIP or 8-lead cerdip. The AD621
also excels in applications requiring high total accuracy, such
as precision data acquisition systems used in weigh scales and
transducer 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
possible total system performance at a lower cost than has been
previously achieved with discrete designs or with other mono-
lithic instrumentation amplifiers.
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.
SOURCE RESISTANCE – H9024
10,000
0.1
1k 100M10k
TOTAL INPUT VOLTAGE NOISE, G = 100
–

H9262
Vp-p
(0.1
–
10Hz)
100k 10M
1,000
100
10
1
1M
TYPICAL STANDARD
BIPOLAR INPUT
IN AMP
AD621 SUPERH9252ETA
BIPOLAR INPUT
IN AMP
Figure 2. Total Voltage Noise vs. Source Resistance
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Fax: 781/326-8703 © Analog Devices, Inc., 2001