®

INA141

8

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 8

Ω 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 0.5

Ω 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 0.2

µVp-p measured

from 0.1 to 10Hz (G = 100). This provides dramatically

improved noise when compared to state-of-the-art chopper-

stabilized amplifiers.

FIGURE 1. Basic Connections.

A

1

A

2

A

3

6

40k

Ω

40k

Ω

40k

Ω

40k

Ω

7

4

3

8

1

2

V

IN

V

IN

V+

V–

INA141

–

+

5

Over-Voltage

Protection

25k

Ω

25k

Ω

Over-Voltage

Protection

Load

V

+

–

0.1µF

0.1µF

+

–

V

O

Also drawn in simplified form:

INA141

Ref

V

O

V

IN

–

V

IN

+

Ref

G = 10

(no connection)

or

G = 100

(connect jumper)

252

Ω

5050

Ω

252

Ω