
Low Cost Low Power
Instrumentation Amplifier
AD620
Rev. H
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FEATURES
Easy to use
Gain set with one external resistor
(Gain range 1 to 10,000)
Wide power supply range (±2.3 V to ±18 V)
Higher performance than 3 op amp IA designs
Available in 8-lead DIP and SOIC packaging
Low power, 1.3 mA max supply current
Excellent dc performance (B grade)
50 μV max, input offset voltage
0.6 μV/°C max, input offset drift
1.0 nA max, input bias current
100 dB min common-mode rejection ratio (G = 10)
Low noise
9 nV/√Hz @ 1 kHz, input voltage noise
0.28 μV p-p noise (0.1 Hz to 10 Hz)
Excellent ac specifications
120 kHz bandwidth (G = 100)
15 μs 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
CONNECTION DIAGRAM
–IN
RG
–VS
+IN
RG
+VS
OUTPUT
REF
1
2
3
4
8
7
6
5
AD620
TOP VIEW
00775-0-001
Figure 1. 8-Lead PDIP (N), CERDIP (Q), and SOIC (R) Packages
PRODUCT DESCRIPTION
The
AD620 is a low cost, high accuracy instrumentation
amplifier that requires only one external resistor to set gains of
1 to 10,000. 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.
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.
Furthermore, 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.
The low input bias current of 1.0 nA max is made possible with
the use of Supereta processing in the input stage. The
AD620works 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,
and 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.
Table 1. Next Generation Upgrades for AD620
Part
Comment
Better specs at lower price
Dual channel or differential out
Low power, wide input range
Best gain accuracy
+2 precision op amps or differential out
Ultra low noise
0
5
10
15
20
30,000
5,000
10,000
15,000
20,000
25,000
0
TO
TAL
ERRO
R,
PPM
O
F
FULL
SCALE
SUPPLY CURRENT (mA)
AD620A
RG
3 OP AMP
IN-AMP
(3 OP-07s)
00775-0-002
Figure 2. Three Op Amp IA Designs vs. AD620