AD626 Datasheet
Single-Supply Differential Amplifier

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Low Cost, Single-Supply
Differential Amplifier
AD626
FEATURES
Pin Selectable Gains of 10 and 100
True Single-Supply Operation
Single-Supply Range of +2.4 V to +10 V
Dual-Supply Range of ؎1.2 V to ؎6 V
Wide Output Voltage Range of 30 mV to 4.7 V
Optional Low-Pass Filtering
Excellent DC Performance
Low Input Offset Voltage: 500 V Max
Large Common-Mode Range: 0 V to +54 V
Low Power: 1.2 mW (VS = +5 V)
Good CMR of 90 dB Typ
AC Performance
Fast Settling Time: 24 s (0.01%)
Includes Input Protection
Series Resistive Inputs (RIN = 200 k)
RFI Filters Included
Allows 50 V Continuous Overload
APPLICATIONS
Current Sensing
Interface for Pressure Transducers, Position Indicators,
Strain Gages, and Other Low Level Signal Sources
PRODUCT DESCRIPTION
The AD626 is a low cost, true single-supply differential amplifier
designed for amplifying and low-pass filtering small differential
voltages from sources having a large common-mode voltage.
The AD626 can operate from either a single supply of +2.4 V to
+10 V, or dual supplies of ±1.2 V to ±6 V.The input common-mode
CONNECTION DIAGRAM
8-Lead Plastic Mini-DIP (N)
and SOIC (R) Packages
–IN 1
ANALOG
GND
2
200k
1/6
G = 30
200k
8 +IN
7 G = 100
–VS 3
FILTER 4
100k
AD626
G=2
6 +VS
5 OUT
range of this amplifier is equal to 6 (+VS – 1 V) which provides a
+24 V CMR while operating from a +5 V supply. Furthermore,
the AD626 features a CMR of 90 dB typ.
The amplifier’s inputs are protected against continuous overload of
up to 50 V, and RFI filters are included in the attenuator network.
The output range is +0.03 V to +4.9 V using a +5 V supply.The
amplifier provides a preset gain of 10, but gains between 10 and
100 can be easily configured with an external resistor. Further-
more, a gain of 100 is available by connecting the G = 100 pin to
analog ground.The AD626 also offers low-pass filter capability by
connecting a capacitor between the filter pin and analog ground.
The AD626A and AD626B operate over the industrial temperature
range of –40°C to +85°C.The AD626 is available in two 8-lead
packages: a plastic mini-DIP and SOIC.
140 25
120
100
G = 10, 100
VS = +5V
80
G = 100
60 VS = ؎5V
40
G = 10
VS = ؎5V
20
0
0.1 1 10 100 1k 10k 100k 1M
FREQUENCY – Hz
20
15 ؎VCM FOR SINGLE
AND DUAL SUPPLIES
10
5 ؎VCM FOR DUAL
SUPPLIES ONLY
0
12 34
SUPPLY VOLTAGE – ؎V
5
Figure 1. Common-Mode Rejection vs. Frequency
REV. D
Figure 2. Input Common-Mode Range vs. Supply
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
that may result from its use. No license is granted by implication or other-
wise under any patent or patent rights of Analog Devices.Trademarks and
registered trademarks are the property of their respective companies.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
www.analog.com
Fax: 781/326-8703
© 2003 Analog Devices, Inc. All rights reserved.


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Single-Supply Differential Amplifier

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AD626* Product Page Quick Links
Last Content Update: 11/01/2016
Comparable Parts
View a parametric search of comparable parts
Documentation
Application Notes
• AN-244: A User's Guide to I.C. Instrumentation Amplifiers
• AN-245: Instrumentation Amplifiers Solve Unusual Design
Problems
• AN-282: Fundamentals of Sampled Data Systems
• AN-589: Ways to Optimize the Performance of a
Difference Amplifier
• AN-671: Reducing RFI Rectification Errors in In-Amp
Circuits
Data Sheet
• AD626: Low Cost, Single Supply Differential Amplifier
Data Sheet
Technical Books
• A Designer's Guide to Instrumentation Amplifiers, 3rd
Edition, 2006
Tools and Simulations
• AD626 SPICE Macro-Model
Reference Materials
Technical Articles
• Auto-Zero Amplifiers
• High-performance Adder Uses Instrumentation Amplifiers
• Input Filter Prevents Instrumentation-amp RF-Rectification
Errors
• The AD8221 - Setting a New Industry Standard for
Instrumentation Amplifiers
Design Resources
• AD626 Material Declaration
• PCN-PDN Information
• Quality And Reliability
• Symbols and Footprints
Discussions
View all AD626 EngineerZone Discussions
Sample and Buy
Visit the product page to see pricing options
Technical Support
Submit a technical question or find your regional support
number
* This page was dynamically generated by Analog Devices, Inc. and inserted into this data sheet. Note: Dynamic changes to
the content on this page does not constitute a change to the revision number of the product data sheet. This content may be
frequently modified.


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IMPORTANT LINKS for the AD626*
Last content update 09/10/2013 07:55 pm
Newer Alternatives: AD8276 or the AD8278 difference amps for their faster speed, smaller foot print, wider supply voltage range, and lower
costs.
PARAMETRIC SELECTION TABLES
Find Similar Products By Operating Parameters
DESIGN COLLABORATION COMMUNITY
DOCUMENTATION
AN-282: Fundamentals of Sampled Data Systems
AN-244: A User’s Guide to I.C. Instrumentation Amplifiers
AN-245: Instrumentation Amplifiers Solve Unusual Design Problems
AN-671: Reducing RFI Rectification Errors in In-Amp Circuits
AN-589: Ways to Optimize the Performance of a Difference Amplifier
A Designer’s Guide to Instrumentation Amplifiers
Auto-Zero Amplifiers
High-performance Adder Uses Instrumentation Amplifiers
Input Filter Prevents Instrumentation-amp RF-Rectification Errors
The AD8221 - Setting a New Industry Standard for Instrumentation
Amplifiers
Applying Instrumentation Amplifiers Effectively: The Importance of an
Input Ground Return
Leading Inside Advertorials: Applying Instrumentation Amplifiers
Effectively—The Importance of an Input Ground Return
Collaborate Online with the ADI support team and other designers
about select ADI products.
Follow us on Twitter: www.twitter.com/ADI_News
Like us on Facebook: www.facebook.com/AnalogDevicesInc
DESIGN SUPPORT
Submit your support request here:
Linear and Data Converters
Embedded Processing and DSP
Telephone our Customer Interaction Centers toll free:
Americas:
1-800-262-5643
Europe:
00800-266-822-82
China:
4006-100-006
India:
1800-419-0108
Russia:
8-800-555-45-90
Quality and Reliability
Lead(Pb)-Free Data
DESIGN TOOLS, MODELS, DRIVERS & SOFTWARE
AD626 SPICE Macro-Model
AD626A SPICE Macro-Model
AD626B SPICE Macro-Model
EVALUATION KITS & SYMBOLS & FOOTPRINTS
Symbols and Footprints
SAMPLE & BUY
AD626
View Price & Packaging
Request Evaluation Board
Request Samples
Check Inventory & Purchase
Find Local Distributors
Powered by TCPDF (www.tcpdf.org)
* This page was dynamically generated by Analog Devices, Inc. and inserted into this data sheet.
Note: Dynamic changes to the content on this page (labeled 'Important Links') does not
constitute a change to the revision number of the product data sheet.
This content may be frequently modified.


AD626 Datasheet
Single-Supply Differential Amplifier

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AD626–SPECIFICATIONS
SINGLE SUPPLY (@+VS = +5 V and TA = 25؇C, unless otherwise noted.)
Model
Parameter
Condition
AD626A
AD626B
Min Typ Max Min Typ Max Unit
GAIN
Gain Accuracy
Gain = 10
Gain = 100
Over Temperature,TA = TMIN to TMAX
Gain Linearity
Gain = 10
Gain = 100
OFFSET VOLTAGE
Input Offset Voltage
vs. Temperature
vs. Temperature
vs. Supply Voltage (PSR)
+PSR
–PSR
Total Error
@ VOUT 100 mV dc
@ VOUT 100 mV dc
G = 10
G = 100
@ VOUT 100 mV dc
@ VOUT 100 mV dc
TMIN to TMAX, G = 10 or 100
TMIN to TMAX, G = 10 or 100
74
64
0.4 1.0
0.1 1.0
50
150
0.014 0.016
0.014 0.02
1.9 2.5
2.9
6
80 74
66 64
0.2 0.6 %
0.5 0.6 %
30 ppm/°C
120 ppm/°C
0.014 0.016 %
0.014 0.02 %
1.9 2.5 mV
2.9 mV
6 µV/°C
80 dB
66 dB
COMMON-MODE REJECTION
+CMR Gain = 10, 100
±CMR Gain = 10, 100
–CMR Gain = 10, 100*
COMMON-MODE VOLTAGE RANGE
+CMV Gain = 10
–CMV Gain = 10
RL = 10 k
f = 100 Hz, VCM = +24 V
f = 10 kHz, VCM = +6 V
f = 100 Hz, VCM = –2 V
CMR > 85 dB
CMR > 85 dB
66
55
60
90
64
85
+24
–2
80 90
55 64
73 85
+24
–2
dB
dB
dB
V
V
INPUT
Input Resistance
Differential
Common-Mode
Input Voltage Range (Common-Mode)
OUTPUT
Output Voltage Swing
Positive
Negative
Short Circuit Current
+ISC
NOISE
Voltage Noise RTI
Gain = 10
Gain = 100
Gain = 10
Gain = 100
RL = 10 k
Gain = 10
Gain = 100
Gain = 10
Gain = 100
f = 0.1 Hz–10 Hz
f = 0.1 Hz–10 Hz
f = 1 kHz
f = 1 kHz
200
100
6 (VS – l)
4.7 4.90
4.7 4.90
0.03
0.03
12
2
2
0.25
0.25
200
100
6 (VS – l)
4.7 4.90
4.7 4.90
0.03
0.03
12
2
2
0.25
0.25
k
k
V
V
V
V
V
mA
µV p-p
µV p-p
µV/ͱHz
µV/ͱHz
DYNAMIC RESPONSE
–3 dB Bandwidth
Slew Rate, TMIN to TMAX
Settling Time
VOUT = +1 V dc
Gain = 10
Gain = 100
to 0.01%, 1 V Step
100
0.17 0.22
0.1 0.17
24
100
0.17 0.22
0.1 0.17
22
kHz
V/µs
V/µs
µs
POWER SUPPLY
Operating Range
Quiescent Current
TA = TMIN to TMAX
Gain = 10
Gain = 100
2.4 5
12 2.4 5
10 V
0.16 0.20
0.16 0.20 mA
0.23 0.29
0.23 0.29 mA
TRANSISTOR COUNT
Number of Transistors
46
46
*At temperatures above 25°C, –CMV degrades at the rate of 12 mV/°C; i.e., @ 25°C CMV = –2 V, @ 85°C CMV = –1.28 V.
Specifications subject to change without notice.
–2– REV. D


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DUAL SUPPLY (@+VS = ؎5 V and TA = 25؇C, unless otherwise noted.)
AD626
Model
Parameter
GAIN
Gain Accuracy
Gain = 10
Gain = 100
Over Temperature,TA = TMIN to TMAX
Gain Linearity
Gain = 10
Gain = 100
OFFSET VOLTAGE
Input Offset Voltage
vs. Temperature
vs. Temperature
vs. Supply Voltage (PSR)
+PSR
–PSR
COMMON-MODE REJECTION
+CMR Gain = 10, 100
±CMR Gain = 10, 100
COMMON-MODE VOLTAGE RANGE
+CMV Gain = 10
–CMV Gain = 10
INPUT
Input Resistance
Differential
Common-Mode
Input Voltage Range (Common-Mode)
OUTPUT
Output Voltage Swing
Positive
Negative
Short Circuit Current
+ISC
–ISC
NOISE
Voltage Noise RTI
Gain = 10
Gain = 100
Gain = 10
Gain = 100
DYNAMIC RESPONSE
–3 dB Bandwidth
Slew Rate, TMIN to TMAX
Settling Time
POWER SUPPLY
Operating Range
Quiescent Current
TRANSISTOR COUNT
Specifications subject to change without notice.
Condition
AD626A
Min Typ Max
Total Error
RL = 10 k
G = 10
G = 100
0.2 0.5
0.25 1.0
50
100
0.045 0.055
0.01 0.015
TMIN to TMAX, G = 10 or 100
TMIN to TMAX, G = 10 or 100
RL = 10 k
f = 100 Hz, VCM = +24 V
f = 10 kHz, VCM = 6 V
74
64
66
55
CMR > 85 dB
CMR > 85 dB
50 500
1.0
1.0
80
66
90
60
26.5
32.5
RL = 10 k
Gain = 10, 100
Gain = 10
Gain = 100
200
110
6 (VS – l)
4.7
–1.65
–1.45
4.90
–2.1
–1.8
12
0.5
f = 0.1 Hz–10 Hz
f = 0.1 Hz–10 Hz
f = 1 kHz
f = 1 kHz
VOUT = +1 V dc
Gain = 10
Gain = 100
to 0.01%, 1 V Step
TA = TMIN to TMAX
Gain = 10
Gain = 100
Number of Transistors
2
2
0.25
0.25
100
0.17 0.22
0.1 0.17
24
Ϯ1.2
Ϯ5
1.5
1.5
46
Ϯ6
2
2
AD626B
Min Typ Max Unit
0.1 0.3 %
0.15 0.6 %
30 ppm/°C
80 ppm/°C
0.045 0.055 %
0.01 0.015 %
50 250 µV
0.5 mV
0.5 µV/°C
74 80
64 66
dB
dB
80 90
55 60
dB
dB
26.5 V
32.5 V
200
110
6 (VS – l)
4.7
–1.65
–1.45
4.90
–2.1
–1.8
12
0.5
k
k
V
V
V
V
mA
mA
2 µV p-p
2 µV p-p
0.25 µV/ͱHz
0.25 µV/ͱHz
100
0.17 0.22
0.1 0.17
22
kHz
V/µs
V/µs
µs
Ϯ1.2
Ϯ5
1.5
1.5
46
Ϯ6 V
2 mA
2 mA
REV. D
–3–


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AD626
ABSOLUTE MAXIMUM RATINGS1
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +36V
Internal Power Dissipation2
Peak Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +60 V
Maximum Reversed Supply Voltage Limit . . . . . . . . . . . . . –34V
Output Short Circuit Duration . . . . . . . . . . . . . . . . . . Indefinite
Storage Temperature Range (N, R) . . . . . . . . . –65°C to +125°C
Operating Temperature Range
AD626A/AD626B . . . . . . . . . . . . . . . . . . . . –40°C to +85°C
Lead Temperature Range (Soldering 60 sec) . . . . . . . . . +300°C
NOTES
1Stresses above those listed under Absolute Maximum Ratings may cause permanent
damage to the device.This is a stress rating only; functional operation of the device
at these or any other conditions above those indicated in the operational section of
this specification is not implied. Exposure to absolute maximum rating conditions
for extended periods may affect device reliability.
2 8-Lead Plastic Package: JA = 100°C/W; JC = 50°C/W.
8-Lead SOIC Package: JA = 155°C/W; JC = 40°C/W.
Model
AD626AN
AD626AR
AD626BN
AD626AR-REEL
AD626AR-REEL7
ORDERING GUIDE
Temperature
Range
Package
Description
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
Plastic DIP
Small Outline IC
Plastic DIP
13" Tape and Reel
7" Tape and Reel
Package
Option
N-8
R-8
N-8
METALLIZATION PHOTOGRAPH
Dimensions shown in inches and (mm).
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate
on the human body and test equipment and can discharge without detection. Although the AD626 features
proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy
electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance
degradation or loss of functionality.
–4–
REV. D


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Typical Performance Characteristics–AD626
25
20
15
10
5
0
1
؎VCM FOR SINGLE
AND DUAL SUPPLIES
؎VCM FOR DUAL
SUPPLIES ONLY
234
SUPPLY VOLTAGE – ؎V
5
6
5
VS = ؎5V
GAIN = 10, 100
4
3
2
1
0
–1
10
100 1k
LOAD RESISTANCE –
10k
TPC 1. Input Common-Mode Range vs. Supply
TPC 4. Positive Output Voltage Swing vs. Resistive Load
5
TA = 25؇C
4
3
SINGLE AND
DUAL SUPPLY
2
DUAL SUPPLY
ONLY
1
0
01234 5
SUPPLY VOLTAGE – V
TPC 2. Positive Output Voltage Swing vs. Supply Voltage
–6
–5
–4
–3 GAIN = 10
–2
GAIN = 100
–1
0
1
100
1k 10k
LOAD RESISTANCE –
100k
TPC 5. Negative Output Voltage Swing vs. Resistive Load
–5
TA = 25؇C
–4
–3
–2
–1
DUAL SUPPLY
ONLY
30
20
10
0
012345
SUPPLY VOLTAGE – V
TPC 3. Negative Output Voltage Swing vs. Supply Voltage
0
0123 45
WARM-UP TIME – Minutes
TPC 6. Change in Input Offset Voltage vs. Warm-UpTime
REV. D
–5–


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1000
GAIN = 100
100
VS = ؎5V
DUAL SUPPLY
VS = +5V
SINGLE SUPPLY
GAIN = 10
10
VS = ؎5V
DUAL SUPPLY
0
10 100 1k 10k 100k 1M
FREQUENCY – Hz
TPC 7. Closed-Loop Gain vs. Frequency
140
120
100
G = 10, 100
VS = +5
80
G = 100
60 VS = ؎5
40
G = 10
VS = ؎5
20
0
0.1
1
10
100
1k
10k 100k
1M
FREQUENCY – Hz
TPC 8. Common-Mode Rejection vs. Frequency
100
G = 10, 100
95
90
85
80
VS = +5
75
70
65
–5
0 5 10 15 20
INPUT COMMON-MODE VOLTAGE – V
25
TPC 9. Common-Mode Rejection vs. Input Common-
Mode Voltage for Single-Supply Operation
100
95
90
85
80
VS = ؎5
75
70
65
20
22 24 26 28
INPUT COMMON-MODE VOLTAGE – V
30
TPC 10. Common-Mode Rejection vs. Input
Common- Mode Voltage for Dual-Supply Operation
100
G = 10, 100
90
80
70
60
0
20 40
60
INPUT SOURCE RESISTANCE MISMATCH –
80
TPC 11. Common-Mode Rejection vs. Input Source
Resistance Mismatch
0.7
CURVE APPLIES TO
0.6
ALL SUPPLY VOLTAGES
AND GAINS BETWEEN 10 AND 100
0.5
TOTAL GAIN ERROR =
0.4 GAIN ACCURACY (FROM SPEC TABLE)
+ ADDITIONAL GAIN ERROR
0.3
0.2
0.1
0.0
10
100
SOURCE RESISTANCE MISMATCH –
TPC 12. Additional Gain Error vs. Source
Resistance Mismatch
1k
–6– REV. D


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0.16
0.15
0.14
G = 10
0.13
0.12
1
23
SUPPLY VOLTAGE – V
4
5
TPC 13. Quiescent Supply Current vs. Supply Voltage
for Single-Supply Operation
2.0
1.5
1.0
0.5
0
؎1 ؎2 ؎3 ؎4 ؎5
SUPPLY VOLTAGE – V
TPC 14. Quiescent Supply Current vs. Supply Voltage
for Dual-Supply Operation
10
1.0
GAIN = 10, 100
0.1
VS = ؎5V DUAL SUPPLY
0.01
1
10 100
1k 10k 100k
FREQUENCY – Hz
TPC 15. Noise Voltage Spectral Density vs. Frequency
AD626
5 SECONDS PER HORIZONTAL DIVISION
TPC 16. 0.1 Hz to 10 Hz RTI Voltage Noise. VS = ±5 V,
Gain = 100
100
80
FOR VS = ؎5V AND +5V
60
40
20
0
1
10 100
1k 10k 100k
VALUE OF RESISTOR RG
TPC 17. Closed-Loop Gain vs. RG
1M
140
ALL CURVES FOR
GAINS OF 10 OR 100
120
100
SINGLE AND DUAL
80 –PSRR
60
40
20
0.1
SINGLE
+PSRR
DDUUAALL
++PPSSRRRR
1 10 100 1k 10k 100k 1M
FREQUENCY – Hz
TPC 18. Power Supply Rejection vs. Frequency
REV. D
–7–


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100
90
100
90
10 10
0% 0%
TPC 19. Large Signal Pulse Response. VS = ±5 V, G = 10
TPC 22. Large Signal Pulse Response. VS = +5 V, G = 100
100 100
90 90
10
0%
TPC 20. Large Signal Pulse Response. VS = ±5 V, G = 100
100
90
10
0%
TPC 23. SettlingTime. VS = ±5 V, G = 10
500mV
100
90
10
0%
TPC 21. Large Signal Pulse Response. VS = +5 V, G = 10
10
0%
TPC 24. SettlingTime. VS = ±5 V, G = 100
–8– REV. D


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AD626
100 100
90 90
10 10
0% 0%
TPC 25. SettlingTime. VS = +5 V, G = 10
TPC 26. SettlingTime. VS = +5 V, G = 100
INPUT
20V p–p
10k
10k
1k
2k
+VS
10k
AD626
ERROR
OUT
–VS
Figure 3. SettlingTimeTest Circuit
THEORY OF OPERATION
The AD626 is a differential amplifier consisting of a precision
balanced attenuator, a very low drift preamplifier (A1), and an
output buffer amplifier (A2). It has been designed so that small
differential signals can be accurately amplified and filtered in the
presence of large common-mode voltages (VCM), without the use
of any other active components.
Figure 4 shows the main elements of the AD626.The signal inputs
at Pins 1 and 8 are first applied to dual resistive attenuators R1
through R4 whose purpose is to reduce the peak common-mode
voltage at the input to the preamplifier—a feedback stage based
on the very low drift op amp A1. This allows the differential
input voltage to be accurately amplified in the presence of large
common-mode voltages six times greater than that which can be
tolerated by the actual input to A1. As a result, the input CMR
extends to six times the quantity (VS – 1 V). The overall common-
mode error is minimized by precise laser-trimming of R3 and R4,
thus giving the AD626 a common-mode rejection ratio (CMRR)
of at least 10,000:1 (80 dB).
To minimize the effect of spurious RF signals at the inputs due to
rectification at the input to A1, small filter capacitors C1 and C2
are included.
The output of A1 is connected to the input of A2 via a 100 k
(R12) resistor to facilitate the low-pass filtering of the signal of
interest (see Low-Pass Filtering section).
The 200 kinput impedance of the AD626 requires that the source
resistance driving this amplifier be low in value (<1 k)—this is
+VS FILTER
C1
R1 5pF
200k
+IN
–IN
R2
200k
R3
41k
A1
C2
5pF
R4
41k
R9
10k
R12
100k
R17
95k
AD626
A2
R15
10k
R11
10k
R6
500
R5
4.2k
R7
500
R8
10k
R10
10k
R14
555
R13
10k
OUT
REV. D
GND
GAIN = 100
Figure 4. Simplified Schematic
–9–
–VS


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AD626
necessary to minimize gain error. Also, any mismatch between the
total source resistance at each input will affect gain accuracy and
common-mode rejection (CMR). For example: when operating at
a gain of 10, an 80 mismatch in the source resistance between
the inputs will degrade CMR to 68 dB.
The output buffer, A2, operates at a gain of 2 or 20, thus setting
the overall, precalibrated gain of the AD626 (with no external
components) at 10 or 100.The gain is set by the feedback network
around amplifier A2.
The output of amplifier A2 relies on a 10 kresistor to –VS for
“pull-down.” For single-supply operation, (–VS = “GND”), A2
can drive a 10 kground referenced load to at least +4.7 V. The
minimum, nominally “zero,” output voltage will be 30 mV. For
dual-supply operation (±5 V), the positive output voltage swing
will be the same as for a single supply. The negative swing will be
to –2.5 V, at G = 100, limited by the ratio:
VS
×
R15 + R14
R13 + R14 + R15
The negative range can be extended to –3.3 V (G = 100) and –4 V
(G = 10) by adding an external 10 kpull-down from the output
to –VS. This will add 0.5 mA to the AD626’s quiescent current,
bringing the total to 2 mA.
The AD626’s 100 kHz bandwidth at G = 10 and 100 (a 10 MHz
gain bandwidth) is much higher than can be obtained with low
power op amps in discrete differential amplifier circuits. Further-
more, the AD626 is stable driving capacitive loads up to 50 pF
(G10) or 200 pF (G100). Capacitive load drive can be increased
to 200 pF (G10) by connecting a 100 resistor in series with the
AD626’s output and the load.
ADJUSTING THE GAIN OF THE AD626
The AD626 is easily configured for gains of 10 or 100. Figure 5
shows that for a gain of 10, Pin 7 is simply left unconnected; simi-
larly, for a gain of 100, Pin 7 is grounded, as shown in Figure 6.
Gains between 10 and 100 are easily set by connecting a variable
resistance between Pin 7 and Analog GND, as shown in Figure 7.
Because the on-chip resistors have an absolute tolerance of ±20%
(although they are ratio matched to within 0.1%), at least a 20%
adjustment range must be provided. The values shown in the
table in Figure 7 provide a good trade-off between gain set range
and resolution, for gains from 11 to 90.
+INPUT
+INPUT
–INPUT
–VS
0.1F
–IN 200k
1
200k+IN
8
ANALOG
2 GND
1/6
G = 30
G = 100 7
3 –VS
100k
FILTER
4
AD626
+VS 6
OUT
G=2
5
+VS
0.1F
OUTPUT
Figure 6. AD626 Configured for a Gain of 100
+INPUT
–INPUT
–IN 200k
1
200k+IN
8
2
ANALOG
GND
1/6
G = 30
RH
G = 100 7
RG
–VS
0.1F
CF
FILTER
(OPTIONAL)
3 –VS
100k
FILTER
4
AD626
+VS 6
OUT
G=2
5
+VS
0.1F
OUTPUT
CORNER FREQUENCY OF FILTER =
1
2CF (100k)
RESISTOR VALUES FOR GAIN ADJUSTMENT
GAIN RANGE
11 – 20
20 – 40
40 – 80
80 – 100
RG()
100k
10k
1k
100
RH()
4.99k
802
80
2
Figure 7. Recommended Circuit for Gain Adjustment
SINGLE-POLE LOW-PASS FILTERING
A low-pass filter can be easily implemented by using the features
provided by the AD626.
By simply connecting a capacitor between Pin 4 and ground,
a single-pole low-pass filter is created, as shown in Figure 8.
+INPUT
–INPUT
–VS
0.1F
–IN 200k
1
200k+IN
8
2 ANALOG
GND
1/6
G = 30
G = 10
7
NOT
CONNECTED
3 –VS
100k
FILTER
4
AD626
+VS 6
OUT
G=2
5
+VS
0.1F
OUTPUT
–INPUT
CF
–IN 200k
1
200k+IN
8
2
ANALOG
GND
1/6
G = 30
G = 100 7
3 –VS
100k
FILTER
4
AD626
+VS 6
OUT
G=2
5
+10V
0.1F
OUTPUT
Figure 5. AD626 Configured for a Gain of 10
CORNER FREQUENCY OF FILTER =
1
2CF (100k)
Figure 8. A One-Pole Low-Pass Filter Circuit
Which Operates from a Single +10 V Supply
–10–
REV. D


AD626 Datasheet
Single-Supply Differential Amplifier

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AD626
CURRENT SENSOR INTERFACE
A typical current sensing application, making use of the large
common-mode range of the AD626, is shown in Figure 9. The
current being measured is sensed across resistor RS. The value of
RS should be less than 1 kand should be selected so that the
average differential voltage across this resistor is typically 100 mV.
To produce a full-scale output of +4 V, a gain of 40 is used adjust-
able by ±20% to absorb the tolerance in the sense resistor. Note
that there is sufficient headroom to allow at least a 10% overrange
(to +4.4 V).
CURRENT IN
CURRENT
SENSOR
RS
–IN 200k
CURRENT OUT
1
200k+IN
8
2
ANALOG
GND
1/6
G = 30
RH
G = 100 7
RG
–VS
0.1F
CF
OPTIONAL
LOW-PASS
FILTER
3 –VS
100k
FILTER
4
AD626
+VS 6
OUT
G=2
5
+VS
0.1F
OUTPUT
Figure 9. Current Sensor Interface
BRIDGE APPLICATION
Figure 10 shows the AD626 in a typical bridge application. Here,
the AD626 is set to operate at a gain of 100, using dual-supply
voltages and offering the option of low-pass filtering.
+VS
–5V
0.1F
CF
OPTIONAL
LOW-PASS
FILTER
–IN 200k
1
200k+IN
8
2
ANALOG
GND
1/6
G = 30
G = 100 7
3 –VS
100k
FILTER
4
AD626
+VS 6
OUT
G=2
5
+5V
0.1F
OUTPUT
Figure 10. ATypical Bridge Application
REV. D
–11–


AD626 Datasheet
Single-Supply Differential Amplifier

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AD626 pdf
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AD626
OUTLINE DIMENSIONS
8-Lead Standard Small Outline Package [SOIC]
Narrow Body
(R-8)
Dimensions shown in millimeters and (inches)
5.00 (0.1968)
4.80 (0.1890)
8
4.00 (0.1574)
3.80 (0.1497) 1
5
6.20 (0.2440)
4 5.80 (0.2284)
0.25 (0.0098)
0.10 (0.0040)
COPLANARITY
0.10
1.27 (0.0500)
BSC
1.75 (0.0688)
1.35 (0.0532)
0.50
0.25
(0.0196)
(0.0099)
؋45؇
SEATING
PLANE
0.51 (0.0201)
0.33 (0.0130)
8؇
0.25 (0.0098) 0؇ 1.27 (0.0500)
0.19 (0.0075) 0.41 (0.0160)
COMPLIANT TO JEDEC STANDARDS MS-012AA
CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
8-Lead Plastic Dual-In Line Package [PDIP]
(N-8)
Dimensions shown in inches and (millimeters)
0.375 (9.53)
0.365 (9.27)
0.355 (9.02)
8 5 0.295 (7.49)
0.285 (7.24)
1 4 0.275 (6.98)
0.100 (2.54)
BSC
0.180
(4.57)
MAX
0.150 (3.81)
0.130 (3.30)
0.110 (2.79)
0.022 (0.56)
0.018 (0.46)
0.014 (0.36)
0.015
(0.38)
MIN
SEATING
PLANE
0.060 (1.52)
0.050 (1.27)
0.045 (1.14)
0.325 (8.26)
0.310 (7.87)
0.300 (7.62)
0.150 (3.81)
0.135 (3.43)
0.120 (3.05)
0.015 (0.38)
0.010 (0.25)
0.008 (0.20)
COMPLIANT TO JEDEC STANDARDS MO-095AA
CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
Revision History
Location
Page
1/03—Data Sheet changed from REV. C to REV. D.
Renumbered Figures and TPCs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Universal
Edits to Figure 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Edits to SPECIFICATIONS, Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Edit to ORDERING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Update to standard CAUTION/ESD Warning note and diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Edits to TPC 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Updated OUTLINE DIMENSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
–12–
REV. D



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