ANALOG DEVICES AD8571, AD8574 Service Manual
Zero-Drift, Single-Supply, Rail-to-Rail
–
O
Input/Output Operational Amplifiers
FEATURES
Low offset voltage: 1 μV
Input offset drift: 0.005 μV/°C
Rail-to-rail input and output swing
5 V/2.7 V single-supply operation
High gain: 145 dB typical
CMRR: 140 dB typical
PSRR: 130 dB typical
Ultralow input bias current: 10 pA typical
Low supply current: 750 μA per op amp
Overload recovery time: 50 μs
No external capacitors required
APPLICATIONS
Temperature sensors
Pressure sensors
Precision current sensing
Strain gage amplifiers
Medical instrumentation
Thermocouple amplifiers
GENERAL DESCRIPTION
This family of amplifiers has ultralow offset, drift, and bias
current. The AD8571, AD8572, and AD8574 are single, dual,
and quad amplifiers, respectively, featuring rail-to-rail input
and output swings. All are guaranteed to operate from 2.7 V to
5 V single supply.
The AD857x family provides benefits previously found only in
expensive auto-zeroing or chopper-stabilized amplifiers. Using
Analog Devices, Inc., topology, these zero-drift amplifiers
combine low cost with high accuracy. (No external capacitors
are required.) Using a patented spread-spectrum, auto-zero
technique, the AD857x family eliminates the intermodulation
effects from interaction of the chopping function with the
signal frequency in ac applications.
With an offset voltage of only 1 µV and drift of 0.005 µV/°C, the
AD857x family is perfectly suited for applications where error
sources cannot be tolerated. Position and pressure sensors,
medical equipment, and strain gage amplifiers benefit greatly
from nearly zero drift over their operating temperature range.
Many more systems require the rail-to-rail input and output
swings provided by the AD857x family.
AD8571/AD8572/AD8574
PIN CONFIGURATIONS
1
NC
AD8571
2
–IN A
+IN A
TOP VIEW
3
(Not to Scale)
V–
4
NC = NO CONNECT
Figure 1. 8-Lead MSOP (RM Suffix)
1
NC
2
IN A
+IN A
AD8571
3
TOP VIEW
(Not to Scale)
V–
4
NC = NO CONNECT
Figure 2. 8-Lead SOIC (R Suffix)
1
OUT A V+
–IN A
+IN A
V–
AD8572
2
TOP VIEW
3
(Not to Scale)
4
Figure 3. 8-Lead TSSOP (RU Suffix)
1
OUT A V+
–IN A
+IN A
V–
AD8572
2
TOP VIEW
3
(Not to Scale)
4
Figure 4. 8-Lead SOIC (R Suffix)
OUT A
1
–IN A
2
+IN A
3
AD8574
V+
4
TOP VIEW
+IN B
–IN B
OUT B
(Not to Scale)
5
6
7
Figure 5. 14-Lead TSSOP (RU Suffix)
OUT A
1
–IN A
2
+IN A
3
AD8574
V+
4
TOP VIEW
UT B
(Not to S cale)
5
6
7
+IN B
–IN B
Figure 6. 14-Lead SOIC (R Suffix)
The AD857x family is specified for the extended industrial/
automotive temperature range (−40°C to +125°C). The AD8571
single amplifier is available in 8-lead MSOP and narrow SOIC
packages. The AD8572 dual amplifier is available in 8-lead narrow
SOIC and surface-mount TSSOP packages. The AD8574 quad
amplifier is available in 14-lead narrow SOIC and TSSOP packages.
8
7
6
5
8
7
6
5
8
7
6
5
8
7
6
5
14
13
12
11
10
9
8
14
13
12
11
10
9
8
NC
V+
OUT A
NC
NC
V+
OUT A
NC
OUT B
–IN B
+IN B
OUT B
–IN B
+IN B
OUT D
–IN D
+IN D
V–
+IN C
–IN C
OUT C
OUT D
–IN D
+IN D
V–
+IN C
–IN C
OUT C
1104-001
01104-004
01104-002
01104-005
01104-003
1104-006
Rev. E
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Anal og Devices for its use, nor for any infringements of patents or ot her
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 www.analog.com
Fax: 781.461.3113 ©1999–2011 Analog Devices, Inc. All rights reserved.
AD8571/AD8572/AD8574
TABLE OF CONTENTS
Features.............................................................................................. 1
Maximizing Performance Through Proper Layout............... 16
Applications....................................................................................... 1
General Description......................................................................... 1
Pin Configurations........................................................................... 1
Revision History ...............................................................................2
Specifications..................................................................................... 3
5 V Electrical Characteristics...................................................... 3
2.7 V Electrical Characteristics................................................... 4
Absolute Maximum Ratings............................................................ 5
Thermal Characteristics ..............................................................5
ESD Caution.................................................................................. 5
Typical Performance Characteristics............................................. 6
Functional Description.................................................................. 14
Amplifier Architecture ..............................................................14
Basic Auto-Zero Amplifier Theory.......................................... 14
Auto-Zero Phase......................................................................... 15
Amplification Phase................................................................... 15
High Gain, CMRR, and PSRR ..................................................16
REVISION HISTORY
2/11—Rev. D to Rev. E
Changes to Figure 66...................................................................... 21
Updated Outline Dimensions....................................................... 22
Changes to Ordering Guide.......................................................... 23
6/08—Rev. C to Rev. D
Changes to Figure 19 and Figure 20............................................... 8
Changes to Figure 44...................................................................... 12
Changes to Figure 38...................................................................... 13
Moved Figure 50 and Figure 51.................................................... 14
Changes to Figure 66, Precision Current Meter Section, Layout,
Figure 67, Equation 24, and Figure 68......................................... 21
5/07—Rev. B to Rev. C
Changes to Features.......................................................................... 1
Changes to Table 1............................................................................ 3
Changes to Table 2............................................................................ 4
Changes to Basic Auto-Zero Amplifier Theory Section ........... 14
Changes to Figure 50...................................................................... 15
Changes to Figure 55...................................................................... 16
Changes to Figure 66...................................................................... 21
Updated Outline Dimensions....................................................... 22
Rev. E | Page 2 of 24
1/f Noise Characteristics ........................................................... 17
Random Auto-Zero Correction Eliminates Intermodulation
Distortion .................................................................................... 17
Broadband and External Resistor Noise Considerations.......... 18
Output Overdrive Recovery...................................................... 18
Input Overvoltage Protection................................................... 18
Output Phase Reversal............................................................... 18
Capacitive Load Drive ............................................................... 19
Power-Up Behavior.................................................................... 19
Applications Information.............................................................. 20
5 V Precision Strain Gage Circuit............................................ 20
3 V Instrumentation Amplifier................................................ 20
High Accuracy Thermocouple Amplifier............................... 21
Precision Current Meter............................................................ 21
Precision Voltage Comparator.................................................. 21
Outline Dimensions....................................................................... 22
Ordering Guide .......................................................................... 23
9/06—Rev. A to Rev. B
Updated Format..................................................................Universal
Changes to Table 1.............................................................................3
Changes to Table 2.............................................................................4
Changes to Figure 50...................................................................... 14
Changes to Figure 51...................................................................... 15
Changes to Figure 66...................................................................... 21
Deleted Figure 69 and SPICE Macro-Model Section ................17
Deleted SPICE Macro-Model for the AD857x Section............. 18
Updated Outline Dimensions....................................................... 22
Changes to Ordering Guide.......................................................... 23
7/03—Rev. 0 to Rev. A
Renumbered Figures..........................................................Universal
Changes to Ordering Guide.............................................................4
Change to Figure 15....................................................................... 16
Updated Outline Dimensions....................................................... 19
10/99—Revision 0: Initial Version
AD8571/AD8572/AD8574
SPECIFICATIONS
5 V ELECTRICAL CHARACTERISTICS
VS = 5 V, VCM = 2.5 V, VO = 2.5 V, TA = 25°C, unless otherwise noted.
Table 1.
Parameter Symbol Conditions Min Typ Max Unit
INPUT CHARACTERISTICS
Offset Voltage VOS 1 5 V
−40°C ≤ TA ≤ +125°C 10 V
Input Bias Current IB 10 50 pA
AD8571/AD8574 −40°C ≤ TA ≤ +125°C 1.0 1.5 nA
AD8572 −40°C ≤ TA ≤ +85°C 160 300 pA
−40°C ≤ TA ≤ +125°C 2.5 4 nA
Input Offset Current IOS 20 70 pA
AD8571/AD8574 −40°C ≤ TA ≤ +125°C 150 200 pA
AD8572 −40°C ≤ TA ≤ +85°C 30 150 pA
−40°C ≤ TA ≤ +125°C 150 400 pA
Input Voltage Range 0 5 V
Common-Mode Rejection Ratio CMRR VCM = 0 V to 5 V 120 140 dB
−40°C ≤ TA ≤ +125°C 115 130 dB
Large Signal Voltage Gain1 A
−40°C ≤ TA ≤ +125°C 120 135 dB
Offset Voltage Drift VOS/T −40°C ≤ TA ≤ +125°C 0.005 0.04 V/°C
OUTPUT CHARACTERISTICS
Output Voltage High VOH R
R
R
R
Output Voltage Low VOL R
R
R
Short-Circuit Limit ISC ±25 ±50 mA
−40°C to +125°C ±40 mA
Output Current IO ±30 mA
−40°C to +125°C ±15 mA
POWER SUPPLY
Power Supply Rejection Ratio PSRR VS = 2.7 V to 5.5 V 120 130 dB
−40°C ≤ TA ≤ +125°C 115 130 dB
Supply Current per Amplifier ISY V
−40°C ≤ TA ≤ +125°C 1000 1075 A
DYNAMIC PERFORMANCE
Slew Rate SR RL = 10 kΩ 0.4 V/s
Overload Recovery Time 0.05 0.3 ms
Gain Bandwidth Product GBP 1.5 MHz
NOISE PERFORMANCE
Voltage Noise en p-p 0 Hz to 10 Hz 1.3 V p-p
0 Hz to 1 Hz 0.41 V p-p
Voltage Noise Density en f = 1 kHz 51 nV/√Hz
Current Noise Density in f = 10 Hz 2 fA/√Hz
1
Gain testing is dependent upon test bandwidth.
R
VO
= 10 kΩ, VO = 0.3 V to 4.7 V 125 145 dB
L
= 100 kΩ to GND 4.99 4.998 V
L
= 100 kΩ to GND @ −40°C to +125°C 4.99 4.997 V
L
= 10 kΩ to GND 4.95 4.98 V
L
= 10 kΩ to GND @ −40°C to +125°C 4.95 4.975 V
L
= 100 kΩ to V+ 1 10 mV
L
= 100 kΩ to V+ @ −40°C to +125°C 2 10 mV
R
L
= 10 kΩ to V+ 10 30 mV
L
= 10 kΩ to V+ @ −40°C to +125°C 15 30 mV
L
= 0 V 850 975 A
O
Rev. E | Page 3 of 24
AD8571/AD8572/AD8574
2.7 V ELECTRICAL CHARACTERISTICS
VS = 2.7 V, VCM = 1.35 V, VO = 1.35 V, TA = 25°C, unless otherwise noted.
Table 2.
Parameter Symbol Conditions Min Typ Max Unit
INPUT CHARACTERISTICS
Offset Voltage VOS 1 5 V
−40°C ≤ TA ≤ +125°C 10 V
Input Bias Current IB 10 50 pA
AD8571/AD8574 −40°C ≤ TA ≤ +125°C 1.0 1.5 nA
AD8572 −40°C ≤ TA ≤ +85°C 160 300 pA
−40°C ≤ TA ≤ +125°C 2.5 4 nA
Input Offset Current IOS 10 50 pA
AD8571/AD8574 −40°C ≤ TA ≤ +125°C 150 200 pA
AD8572 −40°C ≤ TA ≤ +85°C 30 150 pA
−40°C ≤ TA ≤ +125°C 150 400 pA
Input Voltage Range 0 2.7 V
Common-Mode Rejection Ratio CMRR VCM = 0 V to 2.7 V 115 130 dB
−40°C ≤ TA ≤ +125°C 110 130 dB
Large Signal Voltage Gain1 A
−40°C ≤ TA ≤ +125°C 105 130 dB
Offset Voltage Drift VOS/T −40°C ≤ TA ≤ +125°C 0.005 0.04 µV/°C
OUTPUT CHARACTERISTICS
Output Voltage High VOH R
R
R
R
Output Voltage Low VOL R
R
R
R
Short-Circuit Limit ISC ±10 ±15 mA
−40°C to +125°C ±10 mA
Output Current IO ±10 mA
−40°C to +125°C ±5 mA
POWER SUPPLY
Power Supply Rejection Ratio PSRR VS = 2.7 V to 5.5 V 120 130 dB
−40°C ≤ TA ≤ +125°C 115 130 dB
Supply Current per Amplifier ISY V
−40°C ≤ TA ≤ +125°C 950 1000 A
DYNAMIC PERFORMANCE
Slew Rate SR RL = 10 kΩ 0.5 V/s
Overload Recovery Time 0.05 ms
Gain Bandwidth Product GBP 1 MHz
NOISE PERFORMANCE
Voltage Noise en p-p 0 Hz to 10 Hz 2.0 V p-p
Voltage Noise Density en f = 1 kHz 94 nV/√Hz
Current Noise Density in f = 10 Hz 2 fA/√Hz
1
Gain testing is dependent upon test bandwidth.
R
VO
= 10 kΩ, VO = 0.3 V to 2.4 V 110 140 dB
L
= 100 kΩ to GND 2.685 2.697 V
L
= 100 kΩ to GND @ −40°C to +125°C 2.685 2.696 V
L
= 10 kΩ to GND 2.67 2.68 V
L
= 10 kΩ to GND @ −40°C to +125°C 2.67 2.675 V
L
= 100 kΩ to V+ 1 10 mV
L
= 100 kΩ to V+ @ −40°C to +125°C 2 10 mV
L
= 10 kΩ to V+ 10 20 mV
L
= 10 kΩ to V+ @ −40°C to +125°C 15 20 mV
L
= 0 V 750 900 A
O
Rev. E | Page 4 of 24
AD8571/AD8572/AD8574
ABSOLUTE MAXIMUM RATINGS
Table 3.
Parameter Rating
Supply Voltage 6 V
Input Voltage GND to VS + 0.3 V
Differential Input Voltage1 ±5.0 V
ESD (Human Body Model) 2000 V
Output Short-Circuit Duration to GND Indefinite
Storage Temperature Range −65°C to +150°C
Operating Temperature Range −40°C to +125°C
Junction Temperature Range −65°C to +150°C
Lead Temperature (Soldering, 60 sec) 300°C
1
Differential input voltage is limited to ±5.0 V or the supply voltage,
whichever is less.
Stresses 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.
THERMAL CHARACTERISTICS
θJA is specified for the worst-case conditions, that is, θJA is
specified for a device soldered in a circuit board for SOIC and
TSSOP packages.
Table 4. Thermal Resistance
Package Type θJA θ
8-Lead SOIC (R) 158 43 °C/W
8-Lead MSOP (RM) 190 44 °C/W
8-Lead TSSOP (RU) 240 43 °C/W
14-Lead SOIC (R) 120 36 °C/W
14-Lead TSSOP (RU) 180 36 °C/W
Unit
JC
ESD CAUTION
Rev. E | Page 5 of 24
AD8571/AD8572/AD8574
TYPICAL PERFORMANCE CHARACTERISTICS
NUMBER OF AMPL IFIERS
180
160
140
120
100
80
60
40
20
0
–1.5–2.5 –0.5 0.5 1.5 2.5
OFFSET VO LTAGE (µV)
Figure 10. Input Offset Voltage Distribution
VS = 5V
V
= 2.5V
CM
T
= 25°C
A
1104-010
180
160
140
120
100
80
60
NUMBER OF AMPLIFIERS
40
20
0
–1.5–2.5 –0.5 0.5 1.5 2.5
OFFSET VOLTAGE (µV)
VS = 2.7V
V
= 1.35V
CM
T
= 25°C
A
01104-007
Figure 7. Input Offset Voltage Distribution
50
= 5V
V
S
T
= –40°C, +25° C, +85°C
40
A
30
20
10
0
–10
INPUT BIAS CURRENT (pA)
–20
–30
012 435
INPUT COMMO N-MODE VOL TAGE (V)
+85°C
+25°C
–40°C
01104-008
Figure 8. Input Bias Current vs. Input Common-Mode Voltage
1500
V
= 5V
S
T
= 125°C
A
1000
500
0
–500
–1000
INPUT BIAS CURRENT (pA)
–1500
12
10
8
6
4
NUMBER OF AMPLIFIERS
2
0
01234 65
INPUT OFFSET DRIFT (nV/°C)
Figure 11. Input Offset Voltage Drift Distribution
10k
VS = 5V
T
= 25°C
A
1k
100
10
OUTPUT VOLTAGE (mV)
1
SOURCE
VS = 5V
V
= 2.5V
CM
T
= –40°C TO +125°C
A
SINK
1104-011
–2000
012345
COMMON-MODE VOLTAGE (V)
Figure 9. Input Bias Current vs. Common-Mode Voltage
01104-009
Rev. E | Page 6 of 24
0.1
0.0001 0.001 0.01 0. 1 100101
LOAD CURRENT (mA)
Figure 12. Output Voltage to Supply Rail vs. Load Current
01104-012
AD8571/AD8572/AD8574
10k
= 2.7V
V
S
T
= 25°C
A
1k
800
700
600
T
A
= 25°C
100
10
OUTPUT VOL TAGE (mV)
1
0.1
0.0001 0.001 0.01 0. 1 1 10 100
SOURCE
LOAD CURRENT (mA)
SINK
Figure 13. Output Voltage to Supply Rail vs. Load Current
1000
VCM = 2.5V
V
= 5V
S
750
500
250
INPUT BIAS CURRENT (pA)
0
–75 –50 –25 0 25 50 75 100 125 150
TEMPERATURE ( °C)
Figure 14. Input Bias Current vs. Temperature
1.0
0.8
0.6
0.4
SUPPLY CURRENT (mA)
0.2
0
–75 –25–50 25 750 50 100 150125
TEMPERATURE (° C)
5V
2.7V
Figure 15. Supply Current vs. Temperature
500
400
300
200
100
SUPPLY CURRENT PER AMPLIFIER (µA)
0
01 2 34 5 6
01104-013
SUPPLY VOLTAGE (V)
01104-016
Figure 16. Supply Current per Amplifier vs. Supply Voltage
60
VS= 2.7V
C
= 0pF
50
L
R
=
∞
L
40
30
20
10
0
–10
OPEN-LOOP GAIN (dB)
–20
–30
–40
10k 100k 1M 10M 100M
01104-014
FREQUENCY (Hz)
0
45
90
135
180
225
270
PHASE SHIF T (Degrees)
01104-017
Figure 17. Open-Loop Gain and Phase Shift vs. Frequency
60
V
= 5V
S
C
= 0pF
50
L
R
=
∞
L
40
30
20
10
0
–10
OPEN-LOOP GAIN (dB)
–20
–30
–40
10k 100k 1M 10M 100M
01104-015
FREQUENCY (Hz)
0
45
90
135
180
225
270
PHASE SHIFT (Degrees)
01104-018
Figure 18. Open-Loop Gain and Phase Shift vs. Frequency
Rev. E | Page 7 of 24
AD8571/AD8572/AD8574
60
50
40
AV = 100
30
20
= 10
A
V
10
0
AV = 1
–10
CLOSED-LOOP GAIN (dB)
–20
–30
–40
100 10k1k 1M100k 10M
FREQUENCY (Hz)
Figure 19. Closed-Loop Gain vs. Frequency
V
S
C
L
R
L
= 2.7V
= 20pF
= 2kΩ
01104-019
300
VS= 5V
270
240
210
180
150
120
90
OUTPUT IMPEDANCE (Ω)
60
30
0
100 10k1k 10M
FREQUENCY (Hz)
AV = 100
AV = 10
AV = 1
Figure 22. Output Impedance vs. Frequency
1M100k
01104-022
60
50
40
AV = 100
30
20
A
= 10
V
10
0
AV = 1
–10
CLOSED-LOOP GAIN (dB)
–20
–30
–40
100 10k1k 1M100k 10M
FREQUENCY (Hz)
Figure 20. Closed-Loop Gain vs. Frequency
300
VS= 2.7V
270
240
210
180
150
120
90
OUTPUT IM PEDANCE (Ω)
60
30
0
100 10k1k 10M
FREQUENCY (Hz)
AV = 100
AV = 10
AV = 1
Figure 21. Output Impedance vs. Frequency
V
C
R
1M100k
= 5V
S
= 20pF
L
= 2kΩ
L
VS = 2.7V
C
= 300pF
L
R
= 2kΩ
L
A
= 1
V
2µs 500mV
01104-020
1104-023
Figure 23. Large Signal Transient Response
VS = 5V
C
= 300pF
L
R
= 2kΩ
L
A
= 1
V
5µs 1V
1104-021
01104-024
Figure 24. Large Signal Transient Response
Rev. E | Page 8 of 24
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