ANALOG DEVICES AD8682, AD8684 Service Manual
Dual/Quad Low Power, High Speed
www.BDTIC.com/ADI
FEATURES
Low supply current: 250 μA/amp maximum
High slew rate: 9 V/μs
Bandwidth: 3.5 MHz typical
Low offset voltage: 1 mV maximum @ 25°C
Low input bias current: 20 pA maximum @ 25°C
CMRR: 90 dB typical
Fast settling time
Unity gain stable
APPLICATIONS
Portable telecommunications
Low power industrial and instrumentation
Loop filters
Active and precision filters
Integrators
Strain gauge amplifiers
Portable medical instrumentation
Supply current monitoring
JFET Operational Amplifiers
AD8682/AD8684
PIN CONFIGURATIONS
OUT A
1
V–
AD8682
2
TOP VIEW
3
(Not to Scale)
4
–IN A
+IN A
Figure 1. 8-Lead SOIC_N and 8-Lead MSOP
OUT A
1
2
–IN A
+IN A
3
V+
4
AD8684
5
+IN B
6
–IN B
OUT B
7
TOP VIEW
(Not to Scale)
Figure 2. 14-Lead SOIC_N and 14-Lead TSSOP
8
7
6
5
14
13
12
11
10
9
8
V+
OUT B
–IN B
+IN B
OUT D
–IN D
+IN D
V–
+IN C
–IN C
OUT C
6278-001
06278-002
GENERAL DESCRIPTION
The AD8682 and AD8684 are dual and quad low power, precision
(1 mV) JFET amplifiers featuring excellent speed at low supply
currents. The slew rate is typically 9 V/μs with a supply current
under 250 μA per amplifier. These unity-gain stable amplifiers
have a typical gain bandwidth of 3.5 MHz. The JFET input stage
ensures bias current is typically a few picoamps and below 125 pA
maximum over the full temperature operating range.
The devices are ideal for portable, low power applications,
especially with high source impedance. The devices are unity gain
stable and can drive higher capacity loads (G = 1, noninverting),
as an example of their excellent dynamic response over a wide
range of conditions, delivering dc precision performance at low
quiescent currents.
Rev. A
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 ©2006–2007 Analog Devices, Inc. All rights reserved.
AD8682/AD8684
www.BDTIC.com/ADI
TABLE OF CONTENTS
Features.............................................................................................. 1
Applications....................................................................................... 1
Pin Configurations ........................................................................... 1
General Description ......................................................................... 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Electrical Characteristics ............................................................. 3
Absolute Maximum Ratings............................................................ 4
Thermal Resistance ...................................................................... 4
REVISION HISTORY
7/07—Rev. 0 to Rev. A
Change to Figure 21 ......................................................................... 8
Change to Figure 31 ......................................................................... 9
10/06—Revision 0: Initial Version
ESD Caution...................................................................................4
Typical Performance Characteristics..............................................5
Applications Information.............................................................. 10
High-Side Signal Conditioning................................................ 10
Phase Inversion........................................................................... 10
Active Filters ............................................................................... 10
Programmable State Variable Filter ......................................... 11
Outline Dimensions....................................................................... 12
Ordering Guide .......................................................................... 13
Rev. A | Page 2 of 16
AD8682/AD8684
www.BDTIC.com/ADI
SPECIFICATIONS
ELECTRICAL CHARACTERISTICS
VS = ±15.0 V, TA = 25°C, VCM = 0 V, unless otherwise noted.
Table 1.
Parameter Symbol Conditions Min Typ Max Unit
INPUT CHARACTERISTICS
Offset Voltage VOS 0.35 1 mV
AD8682 +25°C ≤ TA ≤ +85°C 2.5 mV
−40°C ≤ TA ≤ +25°C 3 mV
AD8684 +25°C ≤ TA ≤ +85°C 3.5 mV
−40°C ≤ TA ≤ +25°C 4 mV
Input Bias Current IB 6 20 pA
−40°C ≤ TA ≤ +85°C 125 pA
Input Offset Current IOS 20 pA
−40°C ≤ TA ≤ +85°C 100 pA
Input Voltage Range −11 +15 V
Common-Mode Rejection Ratio CMRR −11 V ≤ VCM ≤ +15 V, −40°C ≤ TA ≤ +85°C 70 90 dB
Large Signal Voltage Gain AVO R
R
Offset Voltage Drift ΔVOS/ΔT 10 μV/°C
Bias Current Drift ΔIB/ΔT 8 pA/°C
OUTPUT CHARACTERISTICS
Output Voltage High VOH R
Output Voltage Low VOL R
Short-Circuit Limit ISC Source 3 10 mA
Sink −12 −8 mA
Open-Loop Output Impedance Z
POWER SUPPLY
Power Supply Rejection Ratio PSRR VS = ±4.5 V to ±18 V, −40°C ≤ TA ≤ +85°C 92 114 dB
Supply Current/Amplifier ISY V
Supply Voltage Range VS ±4.5 ±18 V
DYNAMIC PERFORMANCE
Slew Rate SR RL = 10 kΩ 7 9 V/μs
Full-Power Bandwidth BWP 1% distortion 125 kHz
Settling Time tS To 0.01% 1.6 μs
Gain Bandwidth Product GBP 3.5 MHz
Phase Margin ØM 55 Degrees
NOISE PERFORMANCE
Voltage Noise en p-p 0.1 Hz to 10 Hz 1.3 μV p-p
Voltage Noise Density en f = 1 kHz 36 nV/√Hz
Current Noise Density in 0.01 pA/√Hz
f = 1 MHz 200 Ω
OUT
= 10 kΩ 20 V/mV
L
= 10 kΩ, −40°C ≤ TA ≤ +85°C 15 V/mV
L
= 10 kΩ +13.5 +13.9 V
L
= 10 kΩ −13.9 −13.5 V
L
= 0 V, −40°C ≤ TA ≤ +85°C 210 250 μA
O
Rev. A | Page 3 of 16
AD8682/AD8684
www.BDTIC.com/ADI
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter Rating
Supply Voltage ±18 V
Input Voltage ±18 V
Differential Input Voltage1 36 V
Output Short-Circuit Duration Indefinite
Storage Temperature Range −65°C to +150°C
Operating Temperature Range −40°C to +85°C
Junction Temperature Range −65°C to +150°C
Lead Temperature (Soldering, 60 sec) 300°C
1
For supply voltages less than ±18 V, the absolute maximum input voltage is
equal to the supply voltage.
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
Table 3.
Package Type θJA θ
8-Lead MSOP [RM-8] 210 45 °C/W
8-Lead SOIC_N [R-8] 158 43 °C/W
14-Lead TSSOP [RU-14] 180 35 °C/W
14-Lead SOIC [R-14] 120 36 °C/W
ESD CAUTION
Unit
JC
Rev. A | Page 4 of 16
AD8682/AD8684
R
A
www.BDTIC.com/ADI
TYPICAL PERFORMANCE CHARACTERISTICS
80
60
40
20
0
OPEN-LOOP GAIN (dB)
–20
–40
1k
10k 1M 10M100k
FREQUENCY (Hz)
VS = ±15V
T
Figure 3. AD8682 Open-Loop Gain and Phase vs. Frequency
= 25°C
A
180
135
90
45
0
–45
–90
PHASE (Degree)
70
60
50
A
= 100
VCL
40
30
A
= 10
VCL
20
10
A
= 1
VCL
0
CLOSED-LOOP GAIN (dB)
–10
–20
–30
06278-003
1k
10k 1M 10M100k
FREQUENCY ( Hz)
VS = ±15V
= 25°C
T
A
Figure 6. AD8682 Closed-Loop Gain vs. Frequency
06278-006
45
VS = ±15V
40
= 10kΩ
R
L
35
30
25
20
15
OPEN-LOOP GAIN (V/mV)
10
5
0
–75
–25 100 12525
TEMPERATURE (°C)
Figure 4. AD8682 Open-Loop Gain vs. Temperature
80
VS = ±15V
= 2kΩ
R
L
70
= 100mV p-p
V
IN
A
= 1
VCL
T
= 25°C
60
A
50
40
30
OVERSHOOT (%)
20
10
+OS
–OS
30
25
20
TE (V/µs)
15
10
SLEW
5
75500–50
06278-004
0
–75
–25 100 12525
TEMPERATURE (°C)
–SR
+SR
75500–50
VS = ±15V
= 10kΩ
R
L
= 50pF
C
L
06278-007
Figure 7. Slew Rate vs. Temperature
1000
VS = ±15V
= 0V
V
CM
100
10
1
INPUT BIAS CURRENT (pA)
0
0
200 400 500
LOAD CAPACITANCE (pF)
300100
Figure 5. Small Signal Overshoot vs. Load Capacitance
06278-005
0.1
–75
Figure 8. AD8682 Input Bias Current vs. Temperature
Rev. A | Page 5 of 16
–25 100 12525
TEMPERATURE (°C)
75500–50
06278-008
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