Analog Devices AD8698 Service Manual
Dual Precision, Rail-to-Rail Output
FEATURES
Low offset voltage: 100 µV max
Low offset voltage drift: 2 µV/°C max
Low input bias current: 700 pA max
Low noise: 8 nV/√Hz
High common-mode rejection: 118 dB min
Wide operating temperature: −40°C to +85°C
No phase reversal
APPLICATIONS
Photodiode amplifier
Sensors and controls
Multipole filters
Integrator
GENERAL DESCRIPTION
The AD8698 is a high precision, rail-to-rail output, low noise,
low input bias current operational amplifier. Offset voltage is a
respectable 100 µV max and drift over temperature is below
2 µV/°C, eliminating the need for manual offset trimming. The
AD8698 is ideal for high impedance sensors, minimizing offset
errors due to input bias and offset currents.
OUT A
–IN A
+IN A
8-Lead SOIC
1
2
3
(Not to Scale)
V–
4
Operational Amplifier
CONNECTION DIAGRAMS
(R-8)
8
AD8698
TOP VIEW
7
6
5
V+
OUT B
–IN B
+IN B
OUT A
04807-0-069
Figure 1.
–IN A
+IN A
V–
1
2
3
(Not to Scale)
4
AD8698
8-Lead MSOP
(RM-8)
AD8698
TOP VIEW
8
7
6
5
V+
OUT B
–IN B
+IN B
04807-0-070
The rail-to-rail output maximizes dynamic range in a variety of
applications, such as photodiode amplifiers, DAC I/V
amplifiers, filters, and ADC input amplifiers.
The AD8698 dual amplifiers are offered in 8-lead MSOP and
narrow 8-lead SOIC packages. The MSOP version is available
in tape and reel only.
Rev. 0
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: 781.326.8703 © 2004 Analog Devices, Inc. All rights reserved.
AD8698
TABLE OF CONTENTS
Specifications .................................................................................... 3
Instrumentation Amplifier ....................................................... 15
Absolute Maximum Ratings ........................................................... 5
Thermal Resistance ...................................................................... 5
ESD Caution.................................................................................. 5
Typical Performance Characteristics............................................. 6
Applications .................................................................................... 14
Input Overvoltage Protection................................................... 14
Driving Capacitive Loads.......................................................... 14
REVISION HISTORY
4/04—Revision 0: Initial Version
Composite Amplifier ................................................................. 15
Low Noise Applications ............................................................ 16
Driving ADCs............................................................................. 16
Using the AD8698 in Active Filter Designs ........................... 16
Outline Dimensions....................................................................... 17
Ordering Guide .......................................................................... 17
Rev. 0 | Page 2 of 20
AD8698
SPECIFICATIONS
VS = ±15 V, VCM = 0 V (@TA = 25oC, unless otherwise noted.)
Table 1.
Parameter Symbol Conditions Min Typ Max Unit
INPUT CHARACTERISTICS
Offset Voltage VOS 20 100 µV
Offset Voltage Drift
∆V
OS
/∆T
−40°C < T
−40°C < T
< +85°C
A
< +85°C
A
Input Bias Current IB 700 pA
−40°C < T
< +85°C
A
Input Offset Current IOS 700 pA
Input Voltage Range IVR
−40°C < T
−40°C < T
< +85°C
A
< +85°C −13.5V
A
Common-Mode Rejection Ratio CMRR VCM = ±13.5 V 118 132 dB
Large Signal Voltage Gain AVO
Input Capacitance C
C
DIFF
4.6 pF
CM
R
= 2 kΩ, VO = ±13.5 V
L
6.5 pF
OUTPUT CHARACTERISTICS
Output Voltage Swing (Ref. to GND) VOH
V
OH
(Ref. to GND) VOL
VOL
I
= 1 mA, −40°C < TA < +85°C
L
= 5 mA, −40°C < TA < +85°C
I
L
= 1 mA, −40°C < TA < +85°C
I
L
I
= 5 mA, −40°C < TA < +85°C
L
POWER SUPPLY
Power Supply Rejection Ratio PSRR ±2.5 V < VS < ±15 V 114 132 dB
Supply Current ISY V
Supply Voltage VS
= 0 V 2.8 3.2 mA
O
−40°C < T
−40°C < T
< +85°C
A
< +85°C
A
DYNAMIC PERFORMANCE
Slew Rate SR
R
= 2 kΩ
L
Gain Bandwidth Product GBP 1 MHz
Phase Margin ØO 60 Degrees
NOISE PERFORMANCE
Input Noise Voltage en p-p 0.1 Hz < f < 10 Hz 0.6 µV p-p
Input Voltage Noise Density en f = 10 Hz 15
Input Voltage Noise Density en f = 1 kHz 8
Current Noise Density in f = 1 kHz 0.2
300 µV
0.6 2 µV/°C
1500 pA
1500 pA
13.5 V
900 1450 V/mV
14.85 14.93 V
14.6 14.8 V
−14.93 −14.6
−14.82 −14.5
V
V
3.8 mA
±2.5 ±15 V
0.4 V/µs
nV/√Hz
nV/√Hz
pA/√Hz
Rev. 0 | Page 3 of 20
AD8698
VS = ±2.5 V, VCM = 0 V (@TA = 25oC, unless otherwise noted.)
Table 2.
Parameter Symbol Conditions Min Typ Max Unit
INPUT CHARACTERISTICS
Offset Voltage VOS 20 100 µV
Offset Voltage Drift
Input Bias Current IB
∆V
OS
/∆T
−40°C < T
−40°C < T
−40°C < T
< +85°C
A
< +85°C
A
< +85°C
A
Input Offset Current IOS 700 pA
Input Voltage Range IVR
−40°C < T
−40°C < T
< +85°C
A
< +85°C −1.5
A
Common-Mode Rejection Ratio CMRR VCM = ±13.5 V 105 120 dB
Large Signal Voltage Gain AVO
Input Capacitance C
C
6.4 pF
DIFF
4.6 pF
CM
R
= 2 kΩ, VO = ±13.5 V
L
OUTPUT CHARACTERISTICS
Output Voltage Swing (Ref. to GND) VOH
V
OH
(Ref. to GND) VOL
VOL I
I
= 1 mA, −40°C < TA < +85°C
L
I
= 5 mA, −40°C < TA < +85°C
L
= 1 mA, −40°C < TA < +85°C
I
L
= 5 mA, TA = 25°C
L
I
= 5mA, −40°C<TA<+85°C
L
POWER SUPPLY
Power Supply Rejection Ratio PSRR ±2.5 V < VS < ±15 V 114 132 dB
Supply Current ISY V
Supply Voltage Vs
= 0 V 2.3 2.8 mA
O
−40°C < T
−40°C < T
< +85°C
A
< +85°C
A
DYNAMIC PERFORMANCE
Slew Rate SR
R
= 2 kΩ
L
Gain Bandwidth Product GBP 1 MHz
Phase Margin Øo 60 Degrees
NOISE PERFORMANCE
Input Noise Voltage en p-p 0.1 Hz < f < 10Hz 0.6 µV p-p
Input Voltage Noise Density en f = 10 Hz 15
Input Voltage Noise Density en f =1 kHz 8
Current Noise Density in f = 1 kHz 0.2
300 µV
2 µV/°C
700 pA
1500 pA
1500 pA
+1.5 V
600 1200 V/mV
2.35 2.44 V
2.1 2.29 V
−2.43 −2.2
−2.15 −1.9
−1.6
V
V
3.3 mA
±2.5 ±15 V
0.4 V/µs
nV/√Hz
nV/√Hz
pA/√Hz
Rev. 0 | Page 4 of 20
AD8698
ABSOLUTE MAXIMUM RATINGS
Table 3.
Parameter Rating
Supply Voltage ±15 V
Input Voltage ±VS
Differential Input Voltage ±VS
Output Short-Circuit Duration
to Gnd
Storage Temperature Range
R, RM Packages
Operating Temperature Range
Junction Temperature Range
R, RM Packages
Lead Temperature Range
(Soldering, 60 Sec)
Indefinite
−65°C to +150°C
−40°C to +85°C
−65°C to +150°C
+300°C
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 RESISTANCE
θJA is specified for the worst-case conditions, i.e., θJA is specified
for devices soldered in circuit boards for surface-mount
packages.
Table 4. Thermal Resistance
Package Type
MSOP-8 (RM) 210 45 °C/W
SOIC-8 (R) 158 43 °C/W
θJC
θ
JA
Unit
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 1000 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. 0 | Page 5 of 20
AD8698
TYPICAL PERFORMANCE CHARACTERISTICS
NUMBER OF AMPLIFIERS
80
70
60
50
40
30
20
10
VS = ±15V
100
80
60
40
20
GAIN (dB)
0
–20
VS = ±15V
225
180
135
90
45
0
–45
PHASE MARGIN (Degrees)
0
0 0.2 0.4 0.6 0.8 1.0 1.2
TCV
(µV/°C)
OS
Figure 2. Input Offset Voltage Drift Distribution
80
70
60
50
40
30
20
NUMBER OF AMPLIFIERS
10
0
–100 –80 –60 –40 –20 0 40 8020 60 100
V
(µV)
OS
Figure 3. Offset Voltage Distribution
70
60
50
VS = ±15V
VS = ±15V
04807-0-034
04807-0-058
–40
10k 1M100k 10M
FREQUENCY (Hz)
Figure 5. Open-Loop Gain and Phase vs. Frequency
50
40
AV = 100
30
20
AV= 10
10
0
CLOSED-LOOP GAIN (dB)
–10
–20
AV= 1
10k1k 100k 1M 10M
FREQUENCY (Hz)
Figure 6. Closed-Loop Gain vs. Frequency
60
)
45
Ω
VS = ±15V
VS = ±15V
–90
04807-0-001
04807-0-009
40
30
20
NUMBER OF AMPLIFIERS
10
0
–400 –320 –240 –160 –80 0 160 32080 240 400
(pA)
I
B
Figure 4. Input Bias Distribution
04807-0-060
Rev. 0 | Page 6 of 20
30
OUTPUT IMPEDANCE (
15
0
10 100 1k 10k 100k 1M
AV = 100
FREQUENCY (Hz)
AV= 10
AV= 1
Figure 7. Output Impedance vs. Frequency
04807-0-007
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