Datasheet
INA106
6
SBOS152A
www.ti.com
To make a high performance high gain instrumentation amplifier, the INA106
can be combined with state-of-the-art op amps. For low source impedance
applications, OPA37s will give the best noise, offset, and temperature drift. At
source impedances above about 10kΩ, the bias current noise of the OPA37
reacting with input impedance degrades noise. For these applications, use an
OPA111 or a dual OPA2111 FET input op amp for lower noise. For an
electrometer grade IA, use the OPA128—see table below.
Using the INA106 for the difference amplifier also extends the input common-
mode range of the instrumentation amplifier to ±10V. A conventional IA with
a unity-gain difference amplifier has an input common-mode range limited to
±5V for an output swing of ±10V. This is because a unity-gain difference amp
needs ±5V at the input for 10V at the output, allowing only 5V additional for
common-mode.
R
1
R
2
GAIN CMRR NOISE AT 1kHz
A
1
, A
2
(Ω)(kΩ) (V/V) (dB) I
b
(pA) (nV/ √Hz)
OPA37A 50.5 2.5 1000 128 40000 4
OPA111B 202 10 1000 110 1 10
OPA128LM 202 10 1000 118 0.075 38
FIGURE 8. Precision G = 11 Buffer.
FIGURE 3. Difference Amplifier with Gain and CMR Adjust.
FIGURE 4. Precision G = –10 Inverting Amplifier.
This circuit follows an 11/1 divider with a gain of 11 for an overall gain of unity.
With an 11/1 divider, the input signal can exceed 100V without damage.
FIGURE 5. Voltage Follower with Input Protection.
FIGURE 6. Precision Instrumentation Amplifier.
FIGURE 7. Precision Summing Amplifier.
10Ω
10Ω 10kΩ 100kΩ
10kΩ 100kΩ
200Ω
200Ω
V
1
V
2
2
3
5
1
6
E
0
Gain
Adjust
CMR
Adjust
INA106
To eliminate adjustment interactions,
first adjust gain with V
2
grounded.
25
6
INA106
V
O
3
R
3
10kΩ
V
O
= V
IN
V
IN
R
1
10kΩ
R
4
100kΩ
1
R
2
100kΩ
±100V
Safe Input
E
1
–In
2
3
5
1
6
INA106
E
0
= 10(1 + 2R
2
/R
1
) (E
2
– E
1
)
A
2
A
1
E
2
+In
R
1
R
2
E
0
Output
R
2
25
6
INA106
V
0
V
1
R
1
10kΩ
R
4
100kΩ
1
R
2
100kΩ
R
3
10kΩ
3
V
3
V
0
= V
1
+ 10 V
3
5
6
INA106
V
O
= 11V
IN
1
2
V
IN
3
V
O
Gain Error =
0.01% maximum
100kΩ10kΩ
100kΩ
10kΩ
V
2
25
6
INA106
V
O
3
V
O
= –10V
2
1
Gain Error = 0.01% maximum
Nonlinearity = 0.001% maximum
Gain Drift = 2.ppm/°C
10kΩ 100kΩ
10kΩ 100kΩ