INA106

5

SBOS152A

www.ti.com

POWER SUPPLY REJECTION

vs FREQUENCY

Frequency (Hz)

140

120

100

80

60

40

1

10

100

1k

10k

100k

V–

V+

CMR vs FREQUENCY

Frequency (Hz)

110

100

90

80

70

60

10

100

1k

10k

100k

APPLICATIONS INFORMATION

Figure 1 shows the basic connections required for operation

of the INA106. Power supply bypass capacitors should be

connected close to the device pins as shown.

FIGURE 1. Basic Power Supply and Signal Connections.

The differential input signal is connected to pins 2 and 3 as

shown. The source impedance connected to the inputs must

be equal to assure good common-mode rejection. A 5

Ω

mismatch in source impedance will degrade the common-

mode rejection of a typical device to approximately 86dB. If

the source has a known source impedance mismatch, an

additional resistor in series with one input can be used to

preserve good common-mode rejection.

The output is referred to the output reference terminal

(pin 1) which is normally grounded. A voltage applied to the

Ref terminal will be summed with the output signal. The

source impedance of a signal applied to the Ref terminal

should be less than 10

Ω to maintain good common-mode

rejection.

Figure 2 shows a voltage applied to pin 1 to trim the offset

voltage of the INA106. The known 100

Ω source impedance

of the trim circuit is compensated by the 10

Ω resistor in

series with pin 3 to maintain good CMR.

V

2

25

6

INA106

V

1

R

4

100k

Ω

V

3

R

1

10k

Ω

R

3

10k

Ω

3

R

2

100k

Ω

1µF

V–

1µF

V+

47

+

–

FIGURE 2. Offset Adjustment.

V

2

25

6

INA106

V

O

1

R

4

R

1

R

3

3

R

2

499k

Ω

100

Ω

100k

Ω

+15V

–15V

V

3

10

Ω

V

Offset Adjustment Range = ±3mV

Compensates for

some impedance

at pin 1. See text.

Referring to Figure 1, the CMR depends upon the match of

requires resistor matching of 0.005%. To maintain high

CMR over temperature, the resistor TCR tracking must be

better than 2ppm/

°C. These accuracies are difficult and

expensive to reliably achieve with discrete components.