Dual Low Bias Current
Precision Operational Amplifier
OP297
FEATURES PIN CONFIGURATION
Low offset voltage: 50 V maximum
1
OUTA 8 V+
Low offset voltage drift: 0.6 V/C maximum
2
INA 7 OUTB
A B
Very low bias current: 100 pA maximum
+INA 3 6 INB
Very high open-loop gain: 2000 V/mV minimum
4 5
V +INB
Low supply current (per amplifier): 625 A maximum
Figure 1.
Operates from 2 V to 20 V supplies
High common-mode rejection: 120 dB minimum
60
APPLICATIONS
V = 15V
S
V = 0V
CM
Strain gage and bridge amplifiers
40
High stability thermocouple amplifiers
Instrumentation amplifiers
20
Photocurrent monitors
I
B
High gain linearity amplifiers
0
Long-term integrators/filters
I +
B
Sample-and-hold amplifiers
20
Peak detectors
I
OS
Logarithmic amplifiers
40
Battery-powered systems
60
GENERAL DESCRIPTION
75 50 25 0 25 50 75 100 125
TEMPERATURE (C)
The OP297 is the first dual op amp to pack precision perform-
Figure 2. Low Bias Current over Temperature
ance 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
400
1200 UNITS T = 25C
in a wide variety of applications.
A
V = 15V
S
V = 0V
Precision performance of the OP297 includes very low offset
CM
300
(less than 50 V) and low drift (less than 0.6 V/C). Open-
loop gain exceeds 2000 V/mV, ensuring high linearity in every
application.
200
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.
100
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 tempera- 0
100 80 60 40 20 0 20 40 60 80 100
tures. This is in contrast to FET input op amps whose bias
INPUT OFFSET VOLTAGE (V)
currents start in the picoamp range at 25C, but double for
Figure 3. Very Low Offset
every 10C rise in temperature, to reach the nanoamp range
Combining precision, low power, and low bias current, the
above 85C. Input bias current of the OP297 is under 100 pA at
OP297 is ideal for a number of applications, including instru-
25C and is under 450 pA over the military temperature range
mentation amplifiers, log amplifiers, photodiode preamplifiers,
per amplifier. This part can operate with supply voltages as low
and long term integrators. For a single device, see the OP97; for
as 2 V.
a quad device, see the OP497.
Rev. G
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INPUT CURRENT (pA)
NUMBER OF UNITS
00300-001
00300-003
00300-002OP297
TABLE OF CONTENTS
Features .............................................................................................. 1 AC Performance ............................................................................9
Applications ....................................................................................... 1 Guarding and Shielding ................................................................9
General Description ......................................................................... 1 Open-Loop Gain Linearity ....................................................... 10
Pin Configuration ............................................................................. 1 Application Circuits ....................................................................... 11
Revision History ............................................................................... 2 Precision Absolute Value Amplifier ......................................... 11
Specif icat ions ..................................................................................... 3 Precision Current Pump ............................................................ 11
Electrical Characteristics ............................................................. 3 Precision Positive Peak Detector .............................................. 11
Absolute Maximum Ratings ............................................................ 4 Simple Bridge Conditioning Amplifier ................................... 11
Thermal Resistance ...................................................................... 4 Nonlinear Circuits ...................................................................... 12
ESD Caution .................................................................................. 4 Outline Dimensions ....................................................................... 13
Typical Performance Characteristics ............................................. 5 Ordering Guide .......................................................................... 14
Applications Information ................................................................ 9
REVISION HISTORY
4/08Rev. F to Rev. G 10/02Rev. C to Rev. D
Changes to Table 2 Conditions ....................................................... 3 Edits to Figure 16 ............................................................................... 6
Changes to Table 2 Power Supply Rejection Parameter .............. 3
Changes to Figure 5, Figure 6, Figure 7 ......................................... 5 10/02Rev. B to Rev. C
Changes to Figure 16 ........................................................................ 6 Edits to Specifications ....................................................................... 2
Deleted Wafer Test Limits ................................................................ 3
Updated Outline Dimensions ....................................................... 13
Changes to Ordering Guide .......................................................... 14 Deleted Dice Characteristics ............................................................ 3
Deleted Absolute Maximum Ratings .............................................. 4
2/06Rev. E to Rev. F Edits to Ordering Guide ................................................................... 4
Updated Format .................................................................. Universal Updated Outline Dimensions ....................................................... 12
Changes to Features .......................................................................... 1
Deleted OP297 Spice Macro Model Section ................................. 9
Updated Outline Dimensions ....................................................... 13
Changes to Ordering Guide .......................................................... 14
7/03Rev. D to Rev. E
Changes to TPCs 13 and 16 ............................................................ 4
Edits to Figures 12 and 14 ............................................................... 8
Changes to Nonlinear Circuits Section ......................................... 8
Rev. G | Page 2 of 16