INA111AP datasheet(7/17 Pages) TI2

7 / 17 page

INA111

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

Ω in series with the Ref pin will cause a typical

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, RG:

Commonly used gains and resistor values are shown in

Figure 1.

The 50k

Ω 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, RG, also affects gain. RG’s contribution to

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.

FIGURE 1. Basic Connections

DESIRED

NEAREST 1% R

GAIN

(

Ω)(Ω)

No Connection

50.00k

49.9k

12.50k

12.4k

5.556k

5.62k

2.632k

2.61k

1.02k

100

505.1

511

200

251.3

249

500

100.2

100

1000

50.05

49.9

2000

25.01

24.9

5000

10.00

10000

5.001

4.99

= 1 + 50kΩ

(1)

10k

Ω

10k

Ω

10k

Ω

10k

Ω

V+

V–

INA111

G = 1 +

50k

Ω

–

25k

Ω

25k

Ω

Load

O = G • (VIN – VIN)

–

0.1µF

Pin numbers are

for DIP package.

–

INA111

Also drawn in simplified form:

Ref

–

Ref

INA111AP Datasheet(PDF) 7 Page - Texas Instruments

INA111AP Datasheet(HTML) 7 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Datasheet Download

Link URL