INA217

6

SBOS247B

www.ti.com

FIGURE 2. Input Stabilization Network.

V+

V–

V

O

2

1

8

3

5

4

6

7

V

V

INA217

47

Ω

47

Ω

1.2

µH

1.2

µH

APPLICATIONS INFORMATION

Figure 1 shows the basic connections required for operation.

Power supplies should be bypassed with 0.1

µF tantalum

capacitors near the device pins. The output Reference (pin 5)

should be a low-impedance connection. Resistance of a few

ohms in series with this connection will degrade the com-

mon-mode rejection of the INA217.

GAIN-SET RESISTOR

The two internal 5k

Ω feedback resistors are laser-trimmed to

5k

Ω within approximately ±0.2%. The gain equation for the

INA217 is:

G

=+

1

10 000

,

The temperature coefficient of the internal 5k

Ω resistors is

approximately

±25ppm/°C. Accuracy and TCR of the exter-

These effects can be inferred from the gain equation. Make

running output signals near these sensitive input nodes

.

NOISE PERFORMANCE

The INA217 provides very low noise with low-source imped-

ance. Its 1.3nV/

noise performance with a source impedance of 200

Ω. The

input stage design used to achieve this low noise results in

FIGURE 1. Basic Circuit Connections.

relatively high input bias current and input bias current noise.

As a result, the INA217 may not provide the best noise

performance with a source impedance greater than 10k

Ω.

For source impedance greater than 10k

Ω, other instrumen-

tation amplifiers may provide improved noise performance.

INPUT CONSIDERATIONS

Very low source impedance (less than 10

Ω) can cause the

INA217 to oscillate. This depends on circuit layout, signal

source, and input cable characteristics. An input network

consisting of a small inductor and resistor, as shown in

Figure 2, can greatly reduce any tendency to oscillate. This

is especially useful if a variety of input sources are to be

connected to the INA217. Although not shown in other

figures, this network can be used as needed with all applica-

tions shown.

A1

A2

A3

6k

Ω

6k

Ω

6

5

4

7

2

1

8

3

6k

Ω

6k

Ω

V

V

R

G

V+

V–

V+

V–

INA217

G = 1 +

10000

R

G

5k

Ω

5k

Ω

V

OUT

V

O

Sometimes Shown in

Simplified Form:

NOTE: (1) NC = No Connection.

REF

0.1

µF

0.1

µF

R

G

INA217

GAIN

R

G

(V/V)

(dB)

(

Ω)

10

NC

(1)

2

6

10000

5

14

2500

10

20

1111

20

26

526

50

34

204

100

40

101

200

46

50

500

54

20

1000

60

10

2000

66

5

V

V