Datasheet
®
INA111
10
FIGURE 7. Bridge Transducer Amplifier.
mismatched values, causes a high frequency common-mode
signal to be converted to a differential signal. This degrades
common-mode rejection. The differential input capacitor,
C
3
, reduces the bandwidth and mitigates the effects of
mismatch in C
1
and C
2
. Make C
3
much larger than C
1
and
C
2
. If properly matched, C
1
and C
2
also improve CMR.
OUTPUT VOLTAGE SENSE
(SOL-16 Package Only)
The surface-mount version of the INA111 has a separate
output sense feedback connection (pin 12). Pin 12 must be
connected, usually to the output terminal, pin 11, for proper
operation. (This connection is made internally on the DIP
version of the INA111.)
The output feedback connection can be used to sense the
output voltage directly at the load for best accuracy. Figure 8
shows how to drive a load through series interconnection
resistance. Remotely located feedback paths may cause
instability. This can be generally be eliminated with a high
frequency feedback path through C
1
.
FIGURE 6. Input Low-Pass Filter.
FIGURE 8. Remote Load and Ground Sensing.
INA111
R
G
100Ω
V
O
+10V
Bridge
G = 500
Ref
INA111
V
O
V
IN
–
V
IN
+
R
1
R
2
C
3
C
1
C
2
R
1
= R
2
C
1
= C
2
C
3
≈ 10C
1
Ref
INA111
R
G
V
IN
–
V
IN
+
Load
Equal resistance here preserves
g
ood common-mode re
j
ection.
C
1
1000pF
Feedback
Ref
Surface-mount package
version only.
FIGURE 9. High-Pass Input Filter.
INA111
C
1
C
2
R
1
R
2
V
O
2πR
1
C
1
1
f
c
=
NOTE: To preserve good low frequency CMR,
make R
1
= R
2
and C
1
= C
2
.
R
G
Ref
f
−3dB
=
1
4πR
1
C
3
+
C
1
2
FIGURE 10. Galvanically Isolated Instrumentation
Amplifier.
INA111 ISO122
±6V to ±18V
Isolated Power
±15V
Ref
V
IN
–
V
IN
+
V
O
Isolated
Common
V+ V–