Datasheet

"#$
"#%
SBOS051B − OCTOBER 1995 − REVISED FEBRUARY 2005
www.ti.com
11
Operation at very low supply voltage requires careful
attention to assure that the input voltages remain within
their linear range. Voltage swing requirements of
internal nodes limit the input common-mode range with
low power supply voltage. Typical performance curves,
“Input Common-Mode Range vs Output Voltage” show
the range of linear operation for ±15V, ±5V, and ±2.5V
supplies.
300
Ω
+5V
R
G
INA128
V
O
Ref
2.5V − ∆V
2.5V + ∆V
Figure 4. Bridge Amplifier
INA128
R
G
V
O
OPA130
Ref
R
1
1M
Ω
=
1
2
π
R
1
C
1
= 1.59Hz
V
IN
+
f
−3dB
C
1
0.1µF
−
Figure 5. AC-Coupled Instrumentation Amplifier
REF102
R
2
R
1
Pt100
Cu
Cu
V+
K
6
10.0V
4
2
INA128
V
O
Ref
R
G
R3
100Ω = Pt100 at 0°C
SEEBECK
ISA COEFFICIENT
TYPE MATERIAL (µV/5C) R
1
, R
2
E + Chromel 58.5 66.5kΩ
− Constantan
J + Iron 50.2 76.8kΩ
− Constantan
K + Chromel 39.4 97.6kΩ
− Alumel
T + Copper 38.0 102kΩ
− Constantan
Figure 6. Thermocouple Amplifier with RTD
Cold-Junction Compensation
INA128
R
G
I
B
R
1
V
IN
+
A
1
I
O
Load
Ref
I
O
+
V
IN
R
1
@ G
−
A
1
I
B
ERROR
OPA177 ± 1.5nA
OPA131 ± 50pA
OPA602 ± 1pA
OPA128 ± 75fA
Figure 7. Differential Voltage to Current Converter
INA128
R
G
/2
R
G
=5.6k
Ω
V
O
LA
RL
RA
10k
Ω
Ref
G=10
2.8k
Ω
V
G
V
G
2.8k
Ω
1/2
OPA2131
390k
Ω
390k
Ω
1/2
OPA2131
NOTE: Due to the INA128’s current-feedback
topology, V
G
is approximately 0.7V less than
the common-mode input voltage. This DC offset
in this guard potential is satisfactory for many
guarding applications.
Figure 8. ECG Amplifier with Right-Leg Drive