APPLICATION INFORMATION
Figure 1 shows the basic connections required for operation
of the INA141. 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 8Ω in series with the Ref pin will cause a typical
device to degrade to approximately 80dB CMR (G = 1).
SETTING THE GAIN
Gain is selected with a jumper connection as shown in
Figure 1. G = 10V/V with no jumper installed. With a
jumper installed, G = 100V/V. To preserve good gain
accuracy, this jumper must have low series resistance. A
resistance of 0.5Ω in series with the jumper will decrease the
gain by 0.1%.
Internal resistor ratios are laser trimmed to assure excellent
gain accuracy. Actual resistor values can vary by approxi-
mately
±25%
from the nominal values shown.
Gains between 10 and 100 can be achieved by connecting an
external resistor to the jumper pins. This is not recom-
mended, however, because the
±25%
variation of internal
resistor values makes the required external resistor value
uncertain. A companion model, INA128, features accurately
trimmed internal resistors so that gains from 1 to 10,000 can
be set with an external resistor.
DYNAMIC PERFORMANCE
The typical performance curve “Gain vs Frequency” shows
that, despite its low quiescent current, the INA141 achieves
wide bandwidth, even at G = 100. This is due to the current-
feedback topology of the INA141. Settling time also re-
mains excellent at G = 100.
NOISE PERFORMANCE
The INA141 provides very low noise in most applications.
Low frequency noise is approximately 0.2µVp-p measured
from 0.1 to 10Hz (G = 100). This provides dramatically
improved noise when compared to state-of-the-art chopper-
stabilized amplifiers.
V+
0.1µF
7
–
V
IN
2
Over-Voltage
Protection
252Ω
25kΩ
5050Ω
8
252Ω
25kΩ
A
2
40kΩ
40kΩ
5
Ref
A
3
6
–
V
O
= G • (V
IN
– V
IN
)
+
+
INA141
A
1
40kΩ
40kΩ
1
G = 10
(no connection)
or
G = 100
(connect jumper)
Load V
O
–
+
V
IN
3
Over-Voltage
Protection
4
0.1µF
V–
Also drawn in simplified form:
–
V
IN
INA141
+
V
IN
Ref
V
O
FIGURE 1. Basic Connections.
®
INA141
8
TI [ TEXAS INSTRUMENTS ]
