Dual Low Bias Current
Precision Operational Amplifier
OP297
Rev. G
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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
GENERAL DESCRIPTION
The OP297 is the first dual op amp to pack precision perform-
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
in a wide variety of applications.
Precision performance of the OP297 includes very low offset
(less than 50 μV) and low drift (less than 0.6 μV/°C). Open-
loop 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 μA.
The OP297 uses a super-beta input stage with bias current
cancellation to maintain picoamp bias currents at all tempera-
tures. 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.
PIN CONFIGURATION
8
7
6
5
1
2
3
4
OUTA
–INA
+INA
V+
OUTB
–INB
+INB
V–
B
A
00
30
0-
0
01
Figure 1.
TEMPERATURE (°C)
IN
P
UT
CURR
E
NT
(
p
A)
60
–60
40
20
0
–20
–40
–75
–50
–25
0
25
50
75
100
125
IOS
IB+
IB–
VS = ±15V
VCM = 0V
0
030
0-
0
02
Figure 2. Low Bias Current over Temperature
INPUT OFFSET VOLTAGE (V)
NUM
BE
R
O
F
U
NI
T
S
400
0
300
200
100
1200 UNITS
–100 –80
–60
–40
–20
0
20
40
60
80
100
TA = 25°C
VS = ±15V
VCM = 0V
0
0300-
00
3
Figure 3. Very Low Offset
Combining precision, low power, and low bias current, the
OP297 is ideal for a number of applications, including instru-
mentation amplifiers, log amplifiers, photodiode preamplifiers,
and long term integrators. For a single device, see the
OP97; for
a quad device, see the
OP497.