8/21/97 4:00 PM
REV. D
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a
OP297
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700 World Wide Web Site: http://www.analog.com
Fax: 617/326-8703 © Analog Devices, Inc., 1997
Dual Low Bias Current
Precision Operational Amplifier
PIN CONNECTIONS
Plastic Epoxy-DIP (P Suffix)
8-Pin Cerdip (Z Suffix)
8-Pin Narrow Body SOIC (S Suffix)
FEATURES
Precision Performance in Standard SO-8 Pinout
Low Offset Voltage: 50 V max
Low Offset Voltage Drift: 0.6 V/ⴗC max
Very Low Bias Current:
␣ ␣ +25ⴗC (100 pA max)
␣␣–55ⴗC to +125ⴗC (450 pA max)
Very High Open-Loop Gain (2000 V/mV min)
Low Supply Current (Per Amplifier): 625 A max
Operates From 62 V to 620 V Supplies
High Common-Mode Rejection: 120 dB min
Pin Compatible to LT1013, AD706, AD708, OP221,
␣ ␣ LM158, and MC1458/1558 with Improved Performance
APPLICATIONS
Strain Gauge and Bridge Amplifiers
High Stability Thermocouple Amplifiers
Instrumentation Amplifiers
Photo-Current 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 perfor-
mance into the space-saving, industry standard 8-pin SO pack-
age. Its 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,
under 50 µV, and low drift, below 0.6 µV/°C. Open-loop gain
exceeds 2000 V/mV insuring high linearity in every application.
Errors due to common-mode signals are eliminated by the
OP297’s common-mode rejection of over 120 dB. The
OP297’s power supply rejection of over 120 dB minimizes
offset voltage changes experienced in battery powered systems.
Supply current of the OP297 is under 625 µA per amplifier and
it can operate with supply voltages as low as ±2 V.
The OP297 utilizes 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 OP 297 is under 100 pA
at 25°C and is under 450 pA over the military temperature
range.
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, see the OP497.
Figure 1. Low Bias Current Over Temperature Figure 2. Very Low Offset
1
2
3
45
6
7
8
OUT A V+
–IN A OUT B
+IN A –IN B
V– +IN B
+
–
+
–
B
A
TEMPERATURE (°C)
INPUT CURRENT (pA)
60
40
20
0
20
–40
–60
–75 –50 –25 0 25 50 75 100 125
V
S
= ±15V
V
CM
= 0V
I
B
–
I
B
+
I
OS
INPUT OFFSET VOLTAGE (µV)
NUMBER OF UNITS
400
300
200
100
0
–100 –80 –60 –40 –20 0 20 40 60 80 100
1200 UNITS
T
A
= +25°C
V
S
= ±15V
V
CM
= 0V
