INA111_07 BURR-BROWN [Burr-Brown Corporation], INA111_07 Datasheet - Page 7

• Manufacturer Part Number: INA111_07
• Description: High Speed FET-Input INSTRUMENTATION AMPLIFIER
• Manufacturer: BURR-BROWN [Burr-Brown Corporation]

APPLICATION INFORMATION
Figure 1 shows the basic connections required for operation
of the INA111. Applications with noisy or high impedance
power supplies may require decoupling capacitors close to
the device pins as shown.
The output is referred to the output reference (Ref) terminal
which is normally grounded. This must be a low-impedance
connection to assure good common-mode rejection. A resis-
tance of 2
device with 90dB CMR to degrade to approximately 80dB
CMR (G = 1).
SETTING THE GAIN
Gain of the INA111 is set by connecting a single external
resistor, R
Commonly used gains and resistor values are shown in
Figure 1.
FIGURE 1. Basic Connections
G
:
in series with the Ref pin will cause a typical
DESIRED
GAIN
1
2
5
10
20
50
100
200
500
1000
2000
5000
10000
G
No Connection
50.00k
12.50k
5.556k
2.632k
1.02k
505.1
251.3
100.2
50.05
25.01
10.00
5.001
1
( )
R
G
5 0k
R
G
V
V
IN
IN
–
+
NEAREST 1% R
R
No Connection
G
2
1
8
3
49.9k
12.4k
5.62k
2.61k
1.02k
49.9
24.9
4.99
511
249
100
( )
10
for DIP package.
Pin numbers are
G
A
A
1
2
25k
25k
(1)
7
The 50k term in equation 1 comes from the sum of the two
internal feedback resistors. These are on-chip metal film
resistors which are laser trimmed to accurate absolute val-
ues. The accuracy and temperature coefficient of these
resistors are included in the gain accuracy and drift specifi-
cations of the INA111.
The stability and temperature drift of the external gain
setting resistor, R
gain accuracy and drift can be directly inferred from the gain
equation (1). Low resistor values required for high gain can
make wiring resistance important. Sockets add to the wiring
resistance, which will contribute additional gain error (pos-
sibly an unstable gain error) in gains of approximately 100
or greater.
DYNAMIC PERFORMANCE
The typical performance curve “Gain vs Frequency” shows
that the INA111 achieves wide bandwidth over a wide range
of gain. This is due to the current-feedback topology of the
INA111. Settling time also remains excellent over wide
gains.
7
4
10k
10k
V+
V–
0.1µF
0.1µF
INA111
A
10k
10k
3
V
V
G
IN
IN
–
+
, also affects gain. R
Also drawn in simplified form:
R
G
6
5
Ref
INA111
V
G = 1 +
O
= G • (V
Load
INA111
Ref
50k
IN
+
R
V
+
–
G
O
G
– V
’s contribution to
IN
–
V
)
O
®