ANALOG DEVICES AD8672 Service Manual
Precision, Very Low Noise, Low Input
–
+
–
+
FEATURES
Very low noise: 2.8 nV/√Hz, 77 nV p-p
Wide bandwidth: 10 MHz
Low input bias current: 12 nA max
Low offset voltage: 75 μV max
High open-loop gain: 120 dB min
Low supply current: 3 mA typ per amplifier
Dual-supply operation: ±5 V to ±15 V
Unity-gain stable
No phase reversal
APPLICATIONS
PLL filters
Filters for GPS
Instrumentation
Sensors and controls
Professional quality audio
GENERAL DESCRIPTION
The AD8671/AD8672/AD8674 are very high precision amplifiers
featuring very low noise, very low offset voltage and drift, low
input bias current, 10 MHz bandwidth, and low power
consumption. Outputs are stable with capacitive loads of over
1000 pF. Supply current is less than 3 mA per amplifier at 30 V.
The AD8671/AD8672/AD8674’s combination of ultralow noise,
high precision, speed, and stability is unmatched. The MSOP
version of the AD8671/AD8672 requires only half the board
space of comparable amplifiers.
Applications for these amplifiers include high quality PLL
filters, precision filters, medical and analytical instrumentation,
precision power supply controls, ATE, data acquisition, and
precision controls as well as professional quality audio.
The AD8671/AD8672 are specified over the extended industrial
temperature range (−40°C to +125°C), and the AD8674 is specified
over the industrial temperature range (−40°C to +85°C).
Bias Current Operational Amplifiers
AD8671/AD8672/AD8674
PIN CONFIGURATIONS
NC
1
AD8671
2
IN
TOP VIEW
IN
3
(Not to Scale)
V–
4
NC = NO CONNECT
Figure 1. 8-Lead SOIC_N (R-8)
OUT A
1
AD8672
2
–IN A
+IN A
V–
TOP VIEW
3
(Not to Scale)
4
Figure 3. 8-Lead SOIC-N (R-8)
OUT A
1
–IN A
2
3
+IN A
+IN B
–IN B
OUT B
V+
AD8674
4
TOP VIEW
(Not to Scale)
5
6
7
Figure 5. 14-Lead SOIC_N (R-14)
The AD8671, AD8672, and AD8674 are members of a growing
series of low noise op amps offered by Analog Devices, Inc.
Table 1. Voltage Noise
Package 0.9 nV 1.1 nV 1.8 nV 2.8 nV 3.8 nV
Single AD797 AD8597 ADA4004-1 AD8675 AD8671
Dual AD8599 ADA4004-2 AD8676 AD8672
Quad ADA4004-4 AD8674
NC
8
7
V+
OUT
6
NC
5
03718-B-001
NC
1
AD8671
2
IN
TOP VIEW
IN
3
(Not to Scale)
V–
4
NC = NO CONNECT
NC
8
7
V+
OUT
6
NC
5
03718-B-002
Figure 2. 8-Lead MSOP (RM-8)
8
7
6
5
V+
OUT B
–IN B
+IN B
1
V–
AD8672
2
TOP VIEW
3
(Not to Scale)
4
–IN A
+IN A
03718-B-003
8
7
6
5
V+
OUT B
–IN B
+IN B
03718-B-004
OUT A
Figure 4. 8-Lead MSOP (RM-8)
14
13
12
11
10
9
8
OUT D
–IN D
+IN D
V–
+IN C
–IN C
OUT C
1
–IN A
2
+IN A
3
AD8674
V+
4
TOP VIEW
(Not to Scale)
+IN B
5
–IN B
6
OUT B
03718-B-005
7
14
13
12
11
10
9
8
OUT D
–IN D
+IN D
V–
+IN C
–IN C
OUT C
03718-B-006
OUT A
Figure 6. 14-Lead TSSOP (RU-14)
The AD8671/AD8672 are available in the 8-lead SOIC and
8-lead MSOP packages. The AD8674 is available in 14-lead
SOIC and 14-lead TSSOP packages.
Surface-mount devices in MSOP packages are available in tape
and reel only.
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 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 ©2004–2010 Analog Devices, Inc. All rights reserved.
AD8671/AD8672/AD8674
TABLE OF CONTENTS
Specifications ..................................................................................... 3
Output Phase Reversal ............................................................... 12
Electrical Characteristics, ±5.0 V ............................................... 3
Electrical Characteristics, ±15 V ................................................ 4
Absolute Maximum Ratings ............................................................ 5
ESD Caution .................................................................................. 5
Typical Performance Characteristics ............................................. 6
Applications ..................................................................................... 11
Power Dissipation Calculations ................................................ 11
Unity-Gain Follower Applications ........................................... 11
REVISION HISTORY
6/10—Rev. D to Rev. E
Added Table 1 and Preceding Sentence ..................................... 1
12/09—Rev. C to Rev. D
Changes to Features and General Description Sections .......... 1
Changes to Absolute Maximum Ratings Section, Table 3,
and Table 4 ................................................................................ 5
Added Power Dissipation Calculations Section ..................... 11
Updated Outline Dimensions ................................................... 15
Changes to Ordering Guide ...................................................... 17
6/05—Rev. B to Rev. C
Total Noise vs. Source Resistance ............................................. 12
Total Harmonic Distortion (THD) and Noise ....................... 13
Driving Capacitive Loads .......................................................... 13
GPS Receiver ............................................................................... 14
Band-Pass Filter .......................................................................... 14
PLL Synthesizers and Loop Filters ........................................... 14
Outline Dimensions ....................................................................... 15
Ordering Guide .......................................................................... 17
4/04—Rev. A to Rev. B
Changes to Figure 32 .................................................................. 11
Changes to Figures 36, 37, and 38 ............................................ 12
1/04—Rev. 0 to Rev. A
Added AD8672 and AD8674 parts .............................. Universal
Changes to Specifications ............................................................. 3
Deleted Figure 3 ............................................................................. 6
Changes to Figures 7, 8, and 9 ..................................................... 6
Changes to Figure 37 .................................................................. 12
Added new Figure 32 ................................................................. 10
Changes to Figure 6 ...................................................................... 1
Updated Outline Dimensions ................................................... 14
Changes to Ordering Guide ...................................................... 16
Rev. E | Page 2 of 20
AD8671/AD8672/AD8674
SPECIFICATIONS
ELECTRICAL CHARACTERISTICS, ±5.0 V
VS = ±5.0 V, VCM = 0 V, TA = 25°C, unless otherwise noted.
Table 2.
Parameter Symbol Conditions Min Typ Max Unit
INPUT CHARACTERISTICS
Offset Voltage VOS 20 75 μV
–40°C < TA < +125°C 30 125 μV
Offset Voltage Drift ∆VOS/∆T –40°C < TA < +125°C
AD8671 0.3 0.5 μV/°C
AD8672/AD8674 0.3 0.8 μV/°C
Input Bias Current IB –12 +3 +12 nA
+25°C < TA < +125°C –20 +5 +20 nA
–40°C < TA < +125°C –40 +8 +40 nA
Input Offset Current IOS –12 +6 +12 nA
+25°C < TA < +125°C –20 +6 +20 nA
–40°C < TA < +125°C –40 +8 +40 nA
Input Voltage Range –2.5 +2.5 V
Common-Mode Rejection Ratio CMRR VCM = –2.5 V to +2.5 V 100 120 dB
Large Signal Voltage Gain AVO R
Input Capacitance, Common Mode C
Input Capacitance, Differential Mode C
6.25 pF
INCM
7.5 pF
INDM
Input Resistance, Common Mode RIN 3.5 GΩ
Input Resistance, Differential Mode R
15 MΩ
INDM
OUTPUT CHARACTERISTICS
Output Voltage High VOH R
Output Voltage Low VOL R
Output Voltage High VOH R
Output Voltage Low VOL R
Output Current I
±10 mA
OUT
POWER SUPPLY
Power Supply Rejection Ratio PSRR VS = ±4 V to ±18 V
AD8671/AD8672 110 130 dB
AD8674 106 115 dB
Supply Current/Amplifier ISY V
–40°C < TA < +125°C 4.2 mA
DYNAMIC PERFORMANCE
Slew Rate SR RL = 2 kΩ 4 V/μs
Settling Time tS To 0.1% (4 V step, G = 1) 1.4 μs
To 0.01% (4 V step, G = 1) 5.1 μs
Gain Bandwidth Product GBP 10 MHz
NOISE PERFORMANCE
Peak-to-Peak Noise e
0.1 Hz to 10 Hz 77 100 nV p-p
n p-p
Voltage Noise Density en f = 1 kHz 2.8 3.8 nV/√Hz
Current Noise Density in f = 1 kHz 0.3 pA/√Hz
Channel Separation
AD8672/AD8674 CS f = 1 kHz –130 dB
f = 10 kHz –105 dB
= 2 kΩ, VO = –3 V to +3 V 1000 6000 V/mV
L
= 2 kΩ, –40°C to +125°C +3.8 +4.0 V
L
= 2 kΩ, –40°C to +125°C –3.9 –3.8 V
L
= 600 Ω +3.7 +3.9 V
L
= 600 Ω –3.8 –3.7 V
L
= 0 V 3 3.5 mA
O
Rev. E | Page 3 of 20
AD8671/AD8672/AD8674
ELECTRICAL CHARACTERISTICS, ±15 V
VS = ±15 V, VCM = 0 V, TA = 25°C, unless otherwise noted.
Table 3.
Parameter Symbol Conditions Min Typ Max Unit
INPUT CHARACTERISTICS
Offset Voltage VOS 20 75 μV
–40°C < TA < +125°C 30 125 μV
Offset Voltage Drift ∆VOS/∆T –40°C < TA < +125°C
AD8671 0.3 0.5 μV/°C
AD8672/AD8674 0.3 0.8 μV/°C
Input Bias Current IB –12 +3 +12 nA
+25°C < TA < +125°C –20 +5 +20 nA
–40°C < TA < +125°C –40 +8 +40 nA
Input Offset Current IOS –12 +6 +12 nA
+25°C < TA < +125°C –20 +6 +20 nA
–40°C < TA < +125°C –40 +8 +40 nA
Input Voltage Range –12 +12 V
Common-Mode Rejection Ratio CMRR VCM = –12 V to +12 V 100 120 dB
Large Signal Voltage Gain AVO R
Input Capacitance, Common Mode C
Input Capacitance, Differential Mode C
6.25 pF
INCM
7.5 pF
INDM
Input Resistance, Common Mode RIN 3.5 GΩ
Input Resistance, Differential Mode R
15 MΩ
INDM
OUTPUT CHARACTERISTICS
Output Voltage High VOH R
Output Voltage Low VOL R
Output Voltage High VOH R
Output Voltage Low VOL R
Output Current I
±20 mA
OUT
Short Circuit Current ISC ±30 mA
POWER SUPPLY
Power Supply Rejection Ratio PSRR VS = ±4 V to ±18 V
AD8671/AD8672 110 130 dB
AD8674 106 115 dB
Supply Current/Amplifier ISY V
–40°C <TA < +125°C 4.2 mA
DYNAMIC PERFORMANCE
Slew Rate SR RL = 2 kΩ 4 V/μs
Settling Time tS To 0.1% (10 V step, G = 1) 2.2 μs
To 0.01% (10 V step, G = 1) 6.3 μs
Gain Bandwidth Product GBP 10 MHz
NOISE PERFORMANCE
Peak-to-Peak Noise e
0.1 Hz to 10 Hz 77 100 nV p-p
n p-p
Voltage Noise Density en f = 1 kHz 2.8 3.8 nV/√Hz
Current Noise Density in f = 1 kHz 0.3 pA/√Hz
Channel Separation
AD8672/AD8674 CS f = 1 kHz –130 dB
f = 10 kHz –105 dB
= 2 kΩ, VO = –10 V to +10 V 1000 6000 V/mV
L
= 2 kΩ, –40°C to +125°C +13.2 +13.8 V
L
= 2 kΩ, –40°C to +125°C –13.8 –13.2 V
L
= 600 Ω +11 +12.3 V
L
= 600 Ω –12.4 –11 V
L
= 0 V 3 3.5 mA
O
Rev. E | Page 4 of 20
AD8671/AD8672/AD8674
ABSOLUTE MAXIMUM RATINGS
Table 4.1
Parameter Rating
Supply Voltage 36 V
Input Voltage VS– to VS+
Differential Input Voltage ±0.7 V
Output Short-Circuit Duration Indefinite
Storage Temperature Range
All Packages –65°C to +150°C
Operating Temperature Range
8-Lead Packages –40°C to +125°C
14-Lead Packages –40°C to +85°C
Junction Temperature Range
All Packages –65°C to +150°C
Lead Temperature Range (Soldering, 60 sec) 300°C
1
Absolute maximum ratings apply at 25°C, unless otherwise noted.
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.
See the Applications section for a related discussion on power.
Table 5. Package Characteristics
Package Type θ
1
θ
JA
Unit
JC
8-Lead MSOP (RM) 142 44 °C/W
8-Lead SOIC_N (R) 120 43 °C/W
14-Lead SOIC_N (R) 90 36 °C/W
14-Lead TSSOP (RU) 112 35 °C/W
1
θJA is specified for the worst-case conditions, that is., θJA is specified for the
device soldered on a 4-layer circuit board for surface-mount packages.
ESD 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 this product 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.
Rev. E | Page 5 of 20
AD8671/AD8672/AD8674
TYPICAL PERFORMANCE CHARACTERISTICS
32
28
24
20
16
12
8
VOLTAGE NOISE DENSITY (nV/√Hz)
4
0
0 102030405060708090100
FREQUENCY (Hz)
Figure 7. Voltage Noise Density vs. Frequency
VS = ±15V
03718-B-007
NUMBER OF AMPLIFIERS
45
VS = ±5V
T
= 25°C
A
40
35
30
25
20
15
10
5
0
–25 –5–15 0 45–30 –20 –10 5 10 15 20 25 30 35 40
–35
V
OS
Figure 10. Input Offset Voltage Distribution
(μV)
03718-B-010
31.5
27.0
22.5
18.0
13.5
9.0
VOLTAGE NOISE DENSITY (nV/√Hz)
4.5
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
FREQUENCY (kHz)
VS = ±15V
Figure 8. Voltage Noise Density vs. Frequency
VOLTAGE NOISE DENSITY (nV/√Hz)
17.5
15.0
12.5
10.0
7.5
5.0
2.5
0
110234567890
FREQUENCY (kHz)
VS = ±15V
Figure 9. Voltage Noise Density vs. Frequency
35
VS = ±15V
= 25°C
T
A
30
25
20
15
10
NUMBER OF AMPL IFIERS
5
0
–25 –5–15 0 50–30 –20 –10 5 10 15 20 25 30 35 40
–35
03718-B-008
(μV)
V
OS
45
03718-B-011
Figure 11. Input Offset Voltage Distribution
16
15
14
13
V)
μ
12
(
OS
V
11
10
V
= ±5V
S
9
8
7
6
–40 8525 125
03718-B-009
VS = ±15V
TEMPERATURE (°C)
03718-B-012
Figure 12. Input Offset Voltage vs. Temperature
Rev. E | Page 6 of 20
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