ANALOG DEVICES OP297 Service Manual

Dual Low Bias Current

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FEATURES

Low offset voltage: 50 μV maximum
Low offset voltage drift: 0.6 μV/°C maximum
Very low bias current: 100 pA maximum
Very high open-loop gain: 2000 V/mV minimum
Low supply current (per amplifier): 625 μA maximum
Operates from ±2 V to ±20 V supplies
High common-mode rejection: 120 dB minimum

APPLICATIONS

Strain gage and bridge amplifiers
High stability thermocouple amplifiers
Instrumentation amplifiers
Photocurrent monitors
High gain linearity amplifiers
Long-term integrators/filters
Sample-and-hold amplifiers
Peak detectors
Logarithmic amplifiers
Battery-powered systems

Precision Operational Amplifier

OP297

PIN CONFIGURATION

1

OUTA

2

–INA

+INA

A

3

4

Figure 1.

60

40

20

0

–20

INPUT CURRENT (pA)

–40

8

V+

OUTB

7

B

6

–INB

5

+INBV–

00300-001

V

= ±15V

S

V

= 0V

CM

I

–

B

IB+

I

OS

GENERAL DESCRIPTION

The OP297 is the first dual op amp to pack precision perform­ance into the space saving, industry-standard 8-lead SOIC
package. The combination of precision with low power and
extremely low input bias current makes the dual OP297 useful
in a wide variety of applications.

Precision performance of the OP297 includes very low offset
(less than 50 V) and low drift (less than 0.6 V/°C). Open­loop gain exceeds 2000 V/mV, ensuring high linearity in every
application.

Errors due to common-mode signals are eliminated by the
common-mode rejection of over 120 dB, which minimizes
offset voltage changes experienced in battery-powered systems.
The supply current of the OP297 is under 625 A.

The OP297 uses a super-beta input stage with bias current
cancellation to maintain picoamp bias currents at all tempera­tures. This is in contrast to FET input op amps whose bias
currents start in the picoamp range at 25°C, but double for
every 10°C rise in temperature, to reach the nanoamp range
above 85°C. Input bias current of the OP297 is under 100 pA at
25°C and is under 450 pA over the military temperature range
per amplifier. This part can operate with supply voltages as low
as ±2 V.

–60

–75 –50 –25 0 25 50 75 100 125

Figure 2. Low Bias Current over Temperature

TEMPERATURE (° C)

00300-002

400

1200 UNITS

300

200

NUMBER OF UNI TS

100

0

–100 –80 –60 –40 –20 0 20 40 60 80 100

INPUT OFFSET VOLTAGE (µV)

Figure 3. Very Low Offset

T

A

V

S

V

CM

= 25°C
= ±15V

= 0V

00300-003

Combining precision, low power, and low bias current, the
OP297 is ideal for a number of applications, including instru­mentation amplifiers, log amplifiers, photodiode preamplifiers,
and long term integrators. For a single device, see the OP97; for
a quad device, see the OP497.

Rev. G

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] ©2008 Analog Devices, Inc. All rights reserved.

OP297

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TABLE OF CONTENTS

Features .............................................................................................. 1

Applications ....................................................................................... 1 

General Description ......................................................................... 1

Pin Configuration ............................................................................. 1

Revision History ............................................................................... 2

Specifications ..................................................................................... 3

Electrical Characteristics ............................................................. 3

Absolute Maximum Ratings ............................................................ 4

Thermal Resistance ...................................................................... 4

ESD Caution .................................................................................. 4

Typical Performance Characteristics ............................................. 5

Applications Information ................................................................ 9

REVISION HISTORY

4/08—Rev. F to Rev. G

Changes to Table 2 Conditions ....................................................... 3

Changes to Table 2 Power Supply Rejection Parameter .............. 3

Changes to Figure 5, Figure 6, Figure 7 ......................................... 5

Changes to Figure 16 ........................................................................ 6

Updated Outline Dimensions ....................................................... 13

Changes to Ordering Guide .......................................................... 14

2/06—Rev. E to Rev. F

Updated Format .................................................................. Universal

Changes to Features .......................................................................... 1

Deleted OP297 Spice Macro Model Section ................................. 9

Updated Outline Dimensions ....................................................... 13

Changes to Ordering Guide .......................................................... 14

7/03—Rev. D to Rev. E

Changes to TPCs 13 and 16 ............................................................ 4

Edits to Figures 12 and 14 ............................................................... 8

Changes to Nonlinear Circuits Section ......................................... 8

AC Performance ............................................................................9

Guarding and Shielding ................................................................9

Open-Loop Gain Linearity ....................................................... 10

Application Circuits ....................................................................... 11

Precision Absolute Value Amplifier ......................................... 11

Precision Current Pump ............................................................ 11

Precision Positive Peak Detector .............................................. 11

Simple Bridge Conditioning Amplifier ................................... 11

Nonlinear Circuits ...................................................................... 12

Outline Dimensions ....................................................................... 13

Ordering Guide .......................................................................... 14

10/02—Rev. C to Rev. D

Edits to Figure 16 ............................................................................... 6

10/02—Rev. B to Rev. C

Edits to Specifications ....................................................................... 2

Deleted Wafer Test Limits ................................................................ 3

Deleted Dice Characteristics ............................................................ 3

Deleted Absolute Maximum Ratings .............................................. 4

Edits to Ordering Guide ................................................................... 4

Updated Outline Dimensions ....................................................... 12

Rev. G | Page 2 of 16

OP297

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SPECIFICATIONS

ELECTRICAL CHARACTERISTICS

@ VS = ±15 V, TA = 25°C, unless otherwise noted.

Table 1.

OP297E OP297F OP297G
Parameter Symbol Conditions Min Typ Max Min Typ Max Min Typ Max Unit

Input Offset Voltage VOS 25 50 50 100 80 200 µV
Long-Term Input Voltage

Stability
Input Offset Current IOS VCM = 0 V 20 100 35 150 50 200 pA
Input Bias Current IB VCM = 0 V +20 ±100 +35 ±150 +50 ±200 pA
Input Noise Voltage en
Input Noise Voltage Density en f
f
Input Noise Current Density in f
Input Resistance

Differential Mode RIN 30 30 30 MΩ

Common-Mode R
Large Signal Voltage Gain AVO V

Input Voltage Range

1

Common-Mode Rejection CMRR VCM = ±13 V 120 140 114 135 114 135 dB
Power Supply Rejection PSRR VS = ±2 V to

Output Voltage Swing V
R
Supply Current per Amplifier ISY No load 525 625 525 625 525 625 µA
Supply Voltage VS Operating range ±2 ±20 ±2 ±20 ±2 ±20 V
Slew Rate SR 0.05 0.15 0.05 0.15 0.05 0.15 V/µs
Gain Bandwidth Product GBWP AV = +1 500 500 500 kHz
Channel Separation CS V

Input Capacitance CIN 3 3 3 pF

1

Guaranteed by CMR test.

@ V

= ±15 V, −40°C ≤ TA ≤ +85°C, unless otherwise noted.

S

0.1 0.1 0.1 µV/month

0.1 Hz to 10 Hz 0.5 0.5 0.5 V p-p

p-p

= 10 Hz 20 20 20 nV/√Hz

OUT

= 1000 Hz 17 17 17 nV/√Hz

OUT

= 10 Hz 20 20 20 fA/√Hz

OUT

500 500 500 GΩ

INCM

OUT

= 2 kΩ

R

L

= ±10 V,

2000 4000 1500 3200 1200 3200 V/mV

VCM ±13 ±14 ±13 ±14 ±13 ±14 V

120 130 114 125 114 125 dB

±20 V

R

OUT

= 10 kΩ ±13 ±14 ±13 ±14 ±13 ±14 V

L

= 2 kΩ ±13 ±13.7 ±13 ±13.7 ±13 ±13.7 V

L

= 20 V p-p,

OUT

= 10 Hz

f

OUT

150 150 150 dB

Table 2.

OP297E OP297F OP297G
Parameter Symbol Conditions Min Typ Max Min Typ Max Min Typ Max Unit

Input Offset Voltage VOS 35 100 80 300 110 400 V
Average Input Offset Voltage Drift TCVOS 0.2 0.6 0.5 2.0 0.6 2.0 V/°C
Input Offset Current IOS VCM = 0 V 50 450 80 750 80 750 pA
Input Bias Current IB VCM = 0 V +50 ±450 +80 ±750 +80 ±750 pA
Large Signal Voltage Gain AVO V

Input Voltage Range

1

VCM ±13 ±13.5 ±13 ±13.5 ±13 ±13.5 V

OUT

= 2 kΩ

R

L

= ±10 V,

1200 3200 1000 2500 800 2500 V/mV

Common-Mode Rejection CMRR VCM = ±13 114 130 108 130 108 130 dB
Power Supply Rejection PSRR VS = ±2.5 V to

114 108 108 dB

±20 V

Output Voltage Swing V

RL = 10 kΩ ±13 ±13.4 ±13 ±13.4 ±13 ±13.4 V

OUT

Supply Current per Amplifier ISY No load 550 750 550 750 550 750 A
Supply Voltage VS Operating range ±2.5 ±20 ±2.5 ±20 ±2.5 ±20 V

1

Guaranteed by CMR test.

Rev. G | Page 3 of 16

OP297

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ABSOLUTE MAXIMUM RATINGS

Table 3.

Parameter Rating

Supply Voltage ±20 V
Input Voltage1 ±20 V
Differential Input Voltage1 40 V
Output Short-Circuit Duration Indefinite
Storage Temperature Range

Z-Suffix −65°C to +175°C
P-Suffix, S-Suffix −65°C to +150°C

Operating Temperature Range

OP297E (Z-Suffix) −40°C to +85°C
OP297F, OP297G (P-Suffix, S-Suffix) −40°C to +85°C

Junction Temperature

Z-Suffix −65°C to +175°C
P-Suffix, S-Suffix −65°C to +150°C

Lead Temperature (Soldering, 60 sec) 300°C

1

For supply voltages less than ±20 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

θJA is specified for worst-case mounting conditions, that is, θJA
is specified for device in socket for CERDIP and PDIP pack­ages; θ

is specified for device soldered to printed circuit board

JA

for the SOIC package.

Table 4. Thermal Resistance

Package Type θJA θ

Unit

JC

8-Lead CERDIP (Z-Suffix) 134 12 °C/W
8-Lead PDIP (P-Suffix) 96 37 °C/W
8-Lead SOIC (S-Suffix) 150 41 °C/W

ESD CAUTION

–

1/2

OP297

+

50kΩ

50Ω

–

1/2

OP297

+

CHANNEL SEPARATION = 20 l og

Figure 4. Channel Separation Test Circuit

2kΩ

20V p-p @ 10Hz

V

1

V

2

V

1

V2/10000

00300-004

Rev. G | Page 4 of 16

OP297

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TYPICAL PERFORMANCE CHARACTERISTICS

NUMBER OF UNIT S

400

300

200

100

1200 UNITS

T

A

V

S

V

CM

= 25°C
= ±15V

= 0V

60

40

20

–

I

B

0

–20

INPUT CURRENT (p A)

–40

IB+

I

OS

V

S

V

CM

= ±15V

= 0V

0

–100 –80 –60 –40 –20 0 20 40 60 80 100

INPUT OFFSET VO LTAGE (µV)

Figure 5. Typical Distribution of Input Offset Voltage

250

1200 UNITS

200

150

100

NUMBER OF UNITS

50

0

–100 –80 –60 –40 –20 0 20 40 60 80 100

INPUT BIAS CURRENT (pA)

TA = 25°C
V

= ±15V

S

V

CM

Figure 6. Typical Distribution of Input Bias Current

400

1200 UNITS

300

TA = 25°C
V

= ±15V

S

V

CM

= 0V

= 0V

–60

0300-005

–75 –50 –25 0 25 50 75 100 125

TEMPERATURE ( °C)

00300-008

Figure 8. Input Bias, Offset Current vs. Temperature

60

= ±15V

V

S

V

= 0V

CM

40

I

–

B

20

0

INPUT CURRENT (p A)

–20

–40

00300-006

–15 –10 –5 0 5 10 15

COMMON-MODE VOLTAGE (V)

IB+

I

OS

00300-009

Figure 9. Input Bias, Offset Current vs. Common-Mode Voltage

±3

TA = 25°C
V

= ±15V

S

V

= 0V

CM

±2

200

NUMBER OF UNIT S

100

0

–100 –80 –60 –40 –20 0 20 40 60 80 100

INPUT OFFSET CURRENT ( pA)

00300-007

Figure 7. Typical Distribution of Input Offset Current

Rev. G | Page 5 of 16

±1

DEVIATION FROM FI NAL VALUE (µV)

0

01234 5

TIME AFT ER POWER APP LIED (Mi nutes)

Figure 10. Input Offset Voltage Warm-Up Drift

0300-010