ANALOG DEVICES AD8641, AD8643 Service Manual

Low Power, Rail-to-Rail Output

A

A

A

www.BDTIC.com/ADI

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

APPLICATIONS

Line-/battery-powered instruments
Photodiode amplifiers
Precision current sensing
Medical instrumentation
Industrial controls
Precision filters
Portable audio
ATE

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.

Precision JFET Amplifier

AD8641/AD8642/AD8643

PIN CONFIGURATIONS

OUT

1

AD8641

2

VEE

TOP VIEW

(Not to Scale)

+IN

3

Figure 1. 5-Lead SC70 (KS-5)

1

NC

AD8641

2

–IN

3

+IN

TOP VIEW

(Not to Scale)

4

VEE

NC = NO CONNECT

Figure 2. 8-Lead SOIC (R-8)

OUT

1

V–

AD8642

2
3

TOP VIEW

(Not to Scale)

4

–IN A
+IN A

Figure 3. 8-Lead SOIC (R-8)

OUT A

1

V–

AD8642

2

TOP VIEW

3

(Not to Scale)

4

–IN A
+IN A

Figure 4. 8-Lead MSOP (RM-8)

1

OUT

2

–IN A

3

+IN A

+IN B
–IN B

OUT B

V+

AD8643

TOP VIEW

4

(Not to Scale)

5
6
7

Figure 5. 14-Lead SOIC (R-14)

NC

OUT A

161514

1

–IN A
+IN

V+

+IN B

2
3
4

PIN 1
INDICATOR

AD8643

TOP VIEW

5

678

OUT D

NC

13

8
7
6
5

14
13
12
11
10

9
8

5

4

8
7
6
5

8
7
6
5

VCC

–IN

NC
VCC
OUT
NC

V+
OUT B
–IN B
+IN B

V+
OUT B
–IN B
+IN B

OUT D
–IN D
+IN D
V–
+IN C
–IN C
OUT C

12
11
10

9

–IN D
+IN D
V–
+IN C

05072-101

05072-102

05072-064

05072-105

05072-103

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: [phone] www.analog.com
Fax: [phone] ©2005 Analog Devices, Inc. All rights reserved.

Figure 6. 16-Lead LFCSP (CP-16) (Not Drawn to Scale)

–IN B

–IN C

OUT B

NC = NO CONNECT

OUT C

05072-104

AD8641/AD8642/AD8643

www.BDTIC.com/ADI

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

A

dded 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

www.BDTIC.com/ADI

SPECIFICATIONS

ELECTRICAL CHARACTERISTICS

@ VS = 5.0 V, VCM = 2.5 V, TA = 25°C, unless otherwise noted.

Table 1.

Parameter Symbol Conditions Min Typ Max Unit

INPUT CHARACTERISTICS

Offset Voltage V

AD8643 LFCSP only 1 mV
–40°C < TA < +85°C 1.5 mV
+85°C < TA < +125°C, VCM = 1.5 V 1.6 mV

Input Bias Current I

–40°C < TA < +125°C 180 pA

Input Offset Current I
–40°C < TA < +125°C 60 pA

Input Voltage Range 0 3 V

Common-Mode Rejection Ratio CMRR VCM = 0 V to 2.5 V 74 93 dB

Large Signal Voltage Gain A

Offset Voltage Drift ∆VOS/∆T –40°C < TA < +125°C 2.5 µV/°C
OUTPUT CHARACTERISTICS

Output Voltage High V
I

Output Voltage Low V

I

Output Current I
POWER SUPPLY

Power Supply Rejection Ratio PSRR VS = 5 V to 26 V 90 107 dB

Supply Current/Amplifier I
–40°C < TA < +125°C 270 µA
DYNAMIC PERFORMANCE

Slew Rate SR 2 V/µs

Gain Bandwidth Product GBP AD8641, AD8642 3 MHz

AD8643 2.5 MHz

Phase Margin Ø
NOISE PERFORMANCE

Voltage Noise eN p-p f = 0.1 Hz to 10 Hz 4.0 µV p-p

Voltage Noise Density e

Current Noise Density i

OS

B

OS

VO

OH

OL

OUT

SY

m

N

N

50 750 µV

0.25 1 pA

0.5 pA

RL = 10 kΩ, VO = 0.5 to 4.5 V 80 140 V/mV

4.95 V
= 1 mA, –40°C to +125°C 4.94 V

L

0.05 V
= 1 mA, –40°C to +125°C 0.01 0.05 V

L

±6 mA

195 250 µA

50 Degrees

f = 1 kHz 28.5 nV/√Hz
f = 1 kHz 0.5 fA/√Hz

Rev. B | Page 3 of 16

AD8641/AD8642/AD8643

www.BDTIC.com/ADI

@ VS= ±13 V, VCM = 0 V, TA =25°C, unless otherwise noted.

Table 2.

Parameter Symbol Conditions Min Typ Max Unit

INPUT CHARACTERISTICS

Offset Voltage V
AD8643 LFCSP only 1 mV

–40° < TA < +125°C 1.5 mV

Input Bias Current I

–40°C < TA < +125°C 260 pA

Input Offset Current I

–40°C < TA < +125°C 65 pA

Input Voltage Range –13 +10 V
Common-Mode Rejection Ratio CMRR VCM = −13 V to +10 V 90 107 dB
Large Signal Voltage Gain A
Offset Voltage Drift ∆VOS/∆T –40°C < TA < +125°C 2.5 µV/°C

OUTPUT CHARACTERISTICS

Output Voltage High V

I

Output Voltage Low V

I

Output Current I

POWER SUPPLY

Power Supply Rejection Ratio PSRR VS = ±2.5 V to ±13 V 90 107 dB

Supply Current/Amplifier I
–40°C < TA < +125°C 330 µA
DYNAMIC PERFORMANCE

Slew Rate SR 3 V/µs

Gain Bandwidth Product GBP 3.5 MHz

Phase Margin
NOISE PERFORMANCE

Voltage Noise eN p-p f = 0.1 Hz to 10 Hz 4.2 µV p-p

Voltage Noise Density e

Current Noise Density i

OS

B

OS

VO

OH

OL

OUT

SY

Ø

m

N

N

70 750 µV

0.25 1 pA

0.5 pA

RL = 10 kΩ, VO = –11 V to +11 V 215 290 V/mV

+12.95 V

= 1 mA, –40°C to +125°C +12.94 V

L

–12.95 V

= 1 mA, –40°C to +125°C –12.94 V

L

±12 mA

200 290 µA

60 Degrees

f = 1 kHz 27.5 nV/√Hz
f = 1 kHz 0.5 fA/√Hz

Rev. B | Page 4 of 16

AD8641/AD8642/AD8643

www.BDTIC.com/ADI

ABSOLUTE MAXIMUM RATINGS

Table 3.

Parameter Rating

Supply Voltage 27.3 V
Input Voltage VS– to VS+
Differential Input Voltage ±Supply Voltage
Output Short-Circuit Duration Indefinite
Storage Temperature Range

Operating Temperature Range –40°C to +125°C
Junction Temperature Range

Lead Temperature Range (Soldering, 60 sec) 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 listed in the operational sections
of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.

1

KS-5, R-8, RM-8, R-14, CP-16 Packages –65°C to +150°C

KS-5, R-8, RM-8, R-14, CP-16 Packages –65°C to +150°C

Table 4.

Package Type θ

5-Lead SC70 (KS) 331.4 223.9 °C/W
8-Lead SOIC (R) 157 56 °C/W
8-Lead MSOP (RM) 206 44 °C/W
14-Lead SOIC (R) 120 36 °C/W
16-Lead LFCSP (CP) 44 31.5 °C/W

1

Absolute maximum ratings apply at 25°C, unless otherwise noted.

2

θJA is specified for the worst-case conditions, that is, θJA is specified for

devices soldered on circuit boards for surface-mounted packages.

2

JA

θ

JC

Unit

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. B | Page 5 of 16