ISL55004_14 Datasheet, PDF (11/12 Pages) Intersil Corporation – High Supply Voltage 200MHz Unity-Gain Stable Operational Amplifier

ISL55004
Differential Output Instrumentation Amplifier
The addition of a third amplifier to the conventional three
amplifier instrumentation amplifier introduces the benefits of
differential signal realization, specifically the advantage of
using common-mode rejection to remove coupled noise and
ground potential errors inherent in remote transmission. This
configuration also provides enhanced bandwidth, wider
output swing and faster slew rate than conventional three
amplifier solutions with only the cost of an additional
amplifier and few resistors.
A₁
e₁
+
-
R₂
R_G
R₃
R₃
R₃
R₃
A₃
-
e_o3
+
+
R₃
REF
R₃
e_o
e_o3 = –(1 + 2R₂ ⁄ R_G)(e₁ – e₂) e_o4 = (1 + 2R₂ ⁄ R_G)(e₁ – e₂)
e_o = –2(1 + 2R₂ ⁄ R_G)(e₁ – e₂)
BW = ²----^f--^C----¹---^,---²-
A_Di
A_Di = –2(1 + 2R₂ ⁄ R_G)
Strain Gauge
The strain gauge is an ideal application to take advantage of
the moderate bandwidth and high accuracy of the ISL55004.
The operation of the circuit is very straightforward. As the
strain variable component resistor in the balanced bridge is
subjected to increasing strain, its resistance changes,
resulting in an imbalance in the bridge. A voltage variation
from the referenced high accuracy source is generated and
translated to the difference amplifier through the buffer
stage. This voltage difference as a function of the strain is
converted into an output voltage.
R₂
A₄
-
+
-
e_o4
A₂
-
R₃
R₃
e₂
+
FIGURE 30. DIFFERENTIAL OUTPUT AMPLIFIER
VARIABLE SUBJECT
TO STRAIN
V₅ ⁺ R₁₅
0V _- 1kΩ
1kΩ
R₁₆
1kΩ
1kΩ
+ _V2
- ^5V
C₆
1nF
R₁₇ 1kΩ
R₁₈ 1kΩ
+ ^V+
- _V-
R_F
1kΩ
C₁₂
1nF
+ _V4
- ^5V
R_L
V_OUT
(V1+V2+V3+V4)
1kΩ
FIGURE 31. STRAIN GAUGE
11
FN6219.2
July 27, 2006