Low Cost Low Power
Instrumentation Amplifier
AD620
FEATURES
CONNECTION DIAGRAM
Weigh scales
ECG and medical instrumentation
Transducer interface
Data acquisition systems
Industrial process controls
Battery-powered and portable equipment
2
7 +VS
+IN
3
6
–VS
4
AD620
RG
OUTPUT
5 REF
TOP VIEW
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 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,
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.
30,000
TOTAL ERROR, PPM OF FULL SCALE
Comment
Better specs at lower price
Dual channel or differential out
Low power, wide input range
JFET input
Best gain accuracy
+2 precision op amps or differential out
Ultra low noise
8
–IN
Table 1. Next Generation Upgrades for AD620
Part
AD8221
AD8222
AD8226
AD8220
AD8228
AD8295
AD8429
1
25,000
3 OP AMP
IN-AMP
(3 OP-07s)
20,000
15,000
AD620A
10,000
RG
5,000
0
0
5
10
SUPPLY CURRENT (mA)
15
20
00775-0-002
APPLICATIONS
RG
00775-0-001
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%
Figure 2. Three Op Amp IA Designs vs. AD620
Rev. H
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