Low Cost, Low Power
Instrumentation Amplifier
a
AD620
CONNECTION DIAGRAM
FEATURES
EASY TO USE
Gain Set with One External Resistor
(Gain Range 1 to 1000)
8-Lead Plastic Mini-DIP (N), Cerdip (Q)
and SOIC (R) Packages
Wide Power Supply Range (؎2.3 V to ؎18 V)
Higher Performance than Three Op Amp IA Designs
Available in 8-Lead DIP and SOIC Packaging
Low Power, 1.3 mA max Supply Current
1
2
3
4
8
7
6
5
R
R
G
G
+V
–IN
+IN
S
OUTPUT
REF
EXCELLENT DC PERFORMANCE (“B GRADE”)
50 V max, Input Offset Voltage
0.6 V/؇C max, Input Offset Drift
–V
S
AD620
TOP VIEW
1.0 nA max, Input Bias Current
100 dB min Common-Mode Rejection Ratio (G = 10)
1000. Furthermore, the AD620 features 8-lead SOIC and DIP
packaging that is smaller than discrete designs, and offers lower
power (only 1.3 mA max supply current), making it a good fit
for battery powered, portable (or remote) applications.
LOW NOISE
9 nV/√Hz, @ 1 kHz, Input Voltage Noise
0.28 V p-p Noise (0.1 Hz to 10 Hz)
The AD620, with its high accuracy of 40 ppm maximum
nonlinearity, low offset voltage of 50 µV max and offset drift of
0.6 µV/°C max, is ideal for use in precision data acquisition
systems, such as weigh scales and transducer interfaces. Fur-
thermore, the low noise, low input bias current, and low power
of the AD620 make it well suited for medical applications such
as ECG and noninvasive blood pressure monitors.
EXCELLENT AC SPECIFICATIONS
120 kHz Bandwidth (G = 100)
15 s Settling Time to 0.01%
APPLICATIONS
Weigh Scales
ECG and Medical Instrumentation
Transducer Interface
Data Acquisition Systems
Industrial Process Controls
Battery Powered and Portable Equipment
The low input bias current of 1.0 nA max is made possible with
the use of Superβeta processing in the input stage. The AD620
works well as a preamplifier due to its low input voltage noise of
9 nV/√Hz at 1 kHz, 0.28 µV p-p in the 0.1 Hz to 10 Hz band,
0.1 pA/√Hz input current noise. Also, the AD620 is well suited
for multiplexed applications with its settling time of 15 µs to
0.01% and its cost is low enough to enable designs with one in-
amp per channel.
PRODUCT DESCRIPTION
The AD620 is a low cost, high accuracy instrumentation ampli-
fier that requires only one external resistor to set gains of 1 to
30,000
10,000
25,000
20,000
15,000
10,000
5,000
0
3 OP-AMP
IN-AMP
1,000
(3 OP-07s)
TYPICAL STANDARD
BIPOLAR INPUT
IN-AMP
100
G = 100
AD620A
10
R
G
AD620 SUPERETA
BIPOLAR INPUT
1
IN-AMP
0.1
1k
0
5
10
15
20
10k
100k
1M
10M
100M
SUPPLY CURRENT – mA
SOURCE RESISTANCE – ⍀
Figure 1. Three Op Amp IA Designs vs. AD620
Figure 2. Total Voltage Noise vs. Source Resistance
REV. E
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.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
Fax: 781/326-8703
World Wide Web Site: http://www.analog.com
© Analog Devices, Inc., 1999
ADI [ ADI ]
