OP297 Datasheet, PDF (9/16 Pages) Analog Devices – Dual Low Bias Current Precision Operational Amplifier

8/21/97 4:00 PM
PRECISION POSITIVE PEAK DETECTOR
In Figure 32, the C_H must be of polystyrene, Teflon^®*, or poly-
ethylene to minimize dielectric absorption and leakage. The
droop rate is determined by the size of C_H and the bias current
of the OP297.
–
V_IN
+
R₁
10kΩ
R₂
10kΩ
R₃
10kΩ
2_–
1/2
OP-297
3₊
1
R₅
100Ω
+15V
R₄
10kΩ
8 ₊₅
7
1/2
OP-297
–⁶
4
I_OUT
±10mA
I_OUT
=
V_IN
R₅
=
V_IN
100Ω
=
10mA/V
–15V
Figure 31. Precision Current Pump
OP297
SIMPLE BRIDGE CONDITIONING AMPLIFIER
Figure 33 shows a simple bridge conditioning amplifier using
the OP297. The transfer function is:
V _OUT
=
V
REF


R
∆R 
+ ∆R_
R_F
R
The REF43 provides an accurate and stable reference voltage
for the bridge. To maintain the highest circuit accuracy, R_F
should be 0.1% or better with a low temperature coefficient.
1kΩ
2_–
1/2
1
V_IN
1kΩ
OP-297
3₊
1N4148
2N930
C_H
RESET 1kΩ
+15V
0.1µF
6_{– 8}
1/2
7
1kΩ
5
OP-297
+₄
0.1µF
–15V
V_OUT
Figure 32. Precision Positive Peak Detector
+5V
2
REF-43
4
6 2.5V
R
V_REF
R
R
R + ∆R
R_F
2_–
1/2
1
3
OP-297
+
V_OUT
+5V
6_{– 8}
1/2
7
5
OP-297
+₄
( ^∆R
V_OUT = V_{REF R + ∆R}
R_F
R
–5V
Figure 33. A Simple Bridge Conditioning Amplifier Using the OP297
*Teflon is a registered trademark of the Dupont Company
REV. D
–9–