OP297 Analog Devices, OP297 Datasheet - Page 11

• Manufacturer Part Number: OP297
• Description: Dual Low Bias Current Precision Operational Amplifier
• Manufacturer: Analog Devices

Specifications of OP297

• -3db Bandwidth: 500kHz
• Slew Rate: 150mV/µs
• Vos: 80µV
• Ib: 50pA
• # Opamps Per Pkg: 2
• Input Noise (nv/rthz): 17nV/rtHz
• Vcc-vee: 4V to 40V
• Isy Per Amplifier: 625µA
• Packages: DIP,SOIC

APPLICATION CIRCUITS
PRECISION ABSOLUTE VALUE AMPLIFIER
The circuit in Figure 31 is a precision absolute value amplifier
with an input impedance of 30 MΩ. The high gain and low
TCV
input signals. In this circuit, the input always appears as a
common-mode signal to the op amps. The CMR of the OP297
exceeds 120 dB, yielding an error of less than 2 ppm.
V
PRECISION CURRENT PUMP
Maximum output current of the precision current pump shown
in Figure 32 is ±10 mA. Voltage compliance is ±10 V with
±15 V supplies. Output impedance of the current transmitter
exceeds 3 MΩ with linearity better than 16 bits. R1 through R4
should be matched resistors.
IN
V
OS
IN
of the OP297 ensure accurate operation with microvolt
2
3
–
+
OP297
10kΩ
10kΩ
+15V
–15V
R2
R1
1/2
8
4
Figure 31. Precision Absolute Value Amplifier
0.1µF
0.1µF
C2
30pF
C3
10kΩ
C1
2
3
R4
Figure 32. Precision Current Pump
1
–
OP297
+
10kΩ
1/2
R3
7
OP297
+15V
–15V
1/2
1
D1
1N4148
1N4148
8
1kΩ
100kΩ
R1
D2
+
–
R5
5
6
I
OUT
R2
2kΩ
5
6
–
+
OP297
=
1/2
V
R5
1kΩ
IN
R3
=
I
10mA MAX
100Ω
OUT
V
IN
0V < V
7
= 10mA/V
OUT
< 10V
Rev. G | Page 11 of 16
PRECISION POSITIVE PEAK DETECTOR
In Figure 33, the C
polyethylene to minimize dielectric absorption and leakage.
The droop rate is determined by the size of C
current of the OP297.
SIMPLE BRIDGE CONDITIONING AMPLIFIER
Figure 34 shows a simple bridge conditioning amplifier using
the OP297. The transfer function is
The
the bridge. To maintain the highest circuit accuracy, R
be 0.1% or better with a low temperature coefficient.
V
IN
REF43
1kΩ
REF43
V
15V
Figure 34. Simple Bridge Condition Amplifier Using the OP297
OUT
4
2
3
RESET
–
OP297
+
=
provides an accurate and stable reference voltage for
1/2
V
REF
Figure 33. Precision Positive Peak Detector
⎛
⎜
⎝
H
6
5
R
1
V
must be of polystyrene, Teflon®, or
REF
Δ
–
OP297
+
+
1kΩ
R
1/2
Δ
1N4148
R
R + ΔR
8
4
⎞
⎟
⎠
R
R
F
C
7
H
1kΩ
2N930
1kΩ
V
OUT
2
3
+
–
OP297
6
5
= V
1/2
–
OP297
+
–15V
+15V
REF
1/2
R
F
H
0.1µF
0.1µF
R + ΔR
and the bias
ΔR
1
7
R
R
F
OP297
F
V
OUT
should
V
OUT