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Low Power, Rail-to-Rail Output
Precision JFET Amplifier
AD8641/AD8642/AD8643
FEATURES
Low supply current: 250 µA max
Very low input bias current: 1 pA max
Low offset voltage: 750 µV max
Single-supply operation: 5 V to 26 V
Dual-supply operation: ±2.5 V to ±13 V
Rail-to-rail output
Unity-gain stable
No phase reversal
SC70 package
PIN CONFIGURATIONS
OUT
1
5
VCC
AD8641
VEE
2
+IN
3
4
–IN
Figure 1. 5-Lead SC70 (KS-5)
NC
1
–IN
2
+IN
3
VEE
4
8
NC
VCC
OUT
05072-102
05072-104
AD8641
TOP VIEW
(Not to Scale)
7
6
5
NC
APPLICATIONS
Line-/battery-powered instruments
Photodiode amplifiers
Precision current sensing
Medical instrumentation
Industrial controls
Precision filters
Portable audio
ATE
NC = NO CONNECT
Figure 2. 8-Lead SOIC (R-8)
OUT A
1
–IN A
2
+IN A
3
V–
4
8
V+
OUT B
05072-105
05072-103
05072-064
AD8642
TOP VIEW
(Not to Scale)
7
6
5
–IN B
+IN B
Figure 3. 8-Lead SOIC (R-8)
OUT A
1
–IN A
2
8
V+
OUT B
–IN B
+IN B
AD8642
TOP VIEW
(Not to Scale)
7
6
5
GENERAL DESCRIPTION
The AD8641/AD8642/AD8643 are low power, precision JFET
input amplifiers featuring extremely low input bias current and
rail-to-rail output. The ability to swing nearly rail-to-rail at the
input and rail-to-rail at the output enables designers to buffer
CMOS DACs, ASICs, and other wide output swing devices in
single-supply systems. The outputs remain stable with
capacitive loads of more than 500 pF.
The AD8641/AD8642/AD8643 are suitable for applications
utilizing multichannel boards that require low power to manage
heat. Other applications include photodiodes, ATE reference
level drivers, battery management, and industrial controls.
The AD8641/AD8642/AD8643 are fully specified over the
extended industrial temperature range of –40°C to +125°C. The
AD8641 is available in 5-lead SC70 and 8-lead SOIC lead-free
packages. The AD8642 is available in 8-lead MSOP and 8-lead
SOIC lead-free packages. The AD8643 is available in 14-lead
SOIC and 16-lead, 3 mm × 3 mm, LFCSP lead-free packages.
+IN A
3
V–
4
Figure 4. 8-Lead MSOP (RM-8)
OUT A
1
–IN A
2
+IN A
3
V+
4
+IN B
5
–IN B
6
OUT B
7
14
13
OUT D
–IN D
+IN D
AD8643
12
TOP VIEW
11
V–
(Not to Scale)
10
+IN C
9
8
–IN C
OUT C
Figure 5. 14-Lead SOIC (R-14)
OUT A
OUT D
13
NC
NC
16
15
14
–IN A
1
+IN A
2
V+
3
+IN B
4
PIN 1
INDICATOR
12
11
10
9
–IN D
+IN D
V–
+IN C
AD8643
TOP VIEW
–IN B
5
OUT B
6
OUT C
7
NC = NO CONNECT
Figure 6. 16-Lead LFCSP (CP-16) (Not Drawn to Scale)
Rev. B
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
©2005 Analog Devices, Inc. All rights reserved.
–IN C
8
05072-101
TOP VIEW
(Not to Scale)
AD8641/AD8642/AD8643
TABLE OF CONTENTS
Specifications..................................................................................... 3
Electrical Characteristics............................................................. 3
Absolute Maximum Ratings............................................................ 5
ESD Caution.................................................................................. 5
Typical Performance Characteristics ............................................. 6
Outline Dimensions ....................................................................... 13
Ordering Guide........................................................................... 14
REVISION HISTORY
4/05—Rev. A to Rev. B
Added AD8643 ...................................................................Universal
Added 14-Lead SOIC .........................................................Universal
Added 16-Lead LFCSP.......................................................Universal
Updated Outline Dimensions ....................................................... 13
Changes to Ordering Guide .......................................................... 14
3/05—Rev. 0 to Rev. A
Added AD8642 ...................................................................Universal
Changes to General Description .................................................... 1
Added Figure 3 and Figure 4........................................................... 1
Changes to Specifications ................................................................ 3
Changes to Absolute Maximum Ratings ....................................... 5
Changes to Figure 22........................................................................ 8
Changes to Figure 23........................................................................ 9
Changes to Figure 41...................................................................... 12
Updated Outline Dimensions ....................................................... 13
Changes to Ordering Guide .......................................................... 14
10/04—Initial Version: Revision 0
Rev. B | Page 2 of 16
AD8641/AD8642/AD8643
SPECIFICATIONS
ELECTRICAL CHARACTERISTICS
@ V
S
= 5.0 V, V
CM
= 2.5 V, T
A
= 25°C, unless otherwise noted.
Table 1.
Parameter
INPUT CHARACTERISTICS
Offset Voltage
Symbol
V
OS
AD8643 LFCSP only
–40°C < T
A
< +85°C
+85°C < T
A
< +125°C, V
CM
= 1.5 V
Input Bias Current
Input Offset Current
Input Voltage Range
Common-Mode Rejection Ratio
Large Signal Voltage Gain
Offset Voltage Drift
OUTPUT CHARACTERISTICS
Output Voltage High
Output Voltage Low
Output Current
POWER SUPPLY
Power Supply Rejection Ratio
Supply Current/Amplifier
DYNAMIC PERFORMANCE
Slew Rate
Gain Bandwidth Product
Phase Margin
NOISE PERFORMANCE
Voltage Noise
Voltage Noise Density
Current Noise Density
I
B
–40°C < T
A
< +125°C
I
OS
–40°C < T
A
< +125°C
CMRR
A
VO
∆V
OS
/∆T
V
OH
I
L
= 1 mA, –40°C to +125°C
V
OL
I
L
= 1 mA, –40°C to +125°C
I
OUT
PSRR
I
SY
V
S
= 5 V to 26 V
–40°C < T
A
< +125°C
SR
GBP
Ø
m
e
N
p-p
e
N
i
N
f = 0.1 Hz to 10 Hz
f = 1 kHz
f = 1 kHz
2
3
2.5
50
4.0
28.5
0.5
90
0.01
±6
107
195
V
CM
= 0 V to 2.5 V
R
L
= 10 kΩ, V
O
= 0.5 to 4.5 V
–40°C < T
A
< +125°C
0
74
80
93
140
2.5
0.25
Conditions
Min
Typ
50
Max
750
1
1.5
1.6
1
180
0.5
60
3
Unit
µV
mV
mV
mV
pA
pA
pA
pA
V
dB
V/mV
µV/°C
V
V
V
V
mA
dB
µA
µA
V/µs
MHz
MHz
Degrees
µV p-p
nV/√Hz
fA/√Hz
4.95
4.94
0.05
0.05
250
270
AD8641, AD8642
AD8643
Rev. B | Page 3 of 16
AD8641/AD8642/AD8643
@ V
S
= ±13 V, V
CM
= 0 V, T
A
=25°C, unless otherwise noted.
Table 2.
Parameter
INPUT CHARACTERISTICS
Offset Voltage
Symbol
V
OS
AD8643 LFCSP only
–40° < T
A
< +125°C
Input Bias Current
Input Offset Current
Input Voltage Range
Common-Mode Rejection Ratio
Large Signal Voltage Gain
Offset Voltage Drift
OUTPUT CHARACTERISTICS
Output Voltage High
Output Voltage Low
Output Current
POWER SUPPLY
Power Supply Rejection Ratio
Supply Current/Amplifier
DYNAMIC PERFORMANCE
Slew Rate
Gain Bandwidth Product
Phase Margin
NOISE PERFORMANCE
Voltage Noise
Voltage Noise Density
Current Noise Density
I
B
–40°C < T
A
< +125°C
I
OS
–40°C < T
A
< +125°C
CMRR
A
VO
∆V
OS
/∆T
V
OH
I
L
= 1 mA, –40°C to +125°C
V
OL
I
L
= 1 mA, –40°C to +125°C
I
OUT
PSRR
I
SY
V
S
= ±2.5 V to ±13 V
–40°C < T
A
< +125°C
SR
GBP
Ø
m
e
N
p-p
e
N
i
N
f = 0.1 Hz to 10 Hz
f = 1 kHz
f = 1 kHz
3
3.5
60
4.2
27.5
0.5
90
±12
107
200
V
CM
= −13 V to +10 V
R
L
= 10 kΩ, V
O
= –11 V to +11 V
–40°C < T
A
< +125°C
–13
90
215
107
290
2.5
0.25
Conditions
Min
Typ
70
Max
750
1
1.5
1
260
0.5
65
+10
Unit
µV
mV
mV
pA
pA
pA
pA
V
dB
V/mV
µV/°C
V
V
V
V
mA
dB
µA
µA
V/µs
MHz
Degrees
µV p-p
nV/√Hz
fA/√Hz
+12.95
+12.94
–12.95
–12.94
290
330
Rev. B | Page 4 of 16
微控制器 MCU
