A

1

A

2

A

3

40 kW

40 kW

40 kW

40 kW

V

IN

2

1

8

3

6

5

V

IN

R

G

V+

V-

Ref

V

O

G = 1 +

49.4 kW

R

G

+

4

7

INA128, INA129

Over-Voltage

Protection

Over-Voltage

Protection

-

25 kW

(1)

25 kW

(1)

NOTE: (1) INA129: 24.7 kW

G = 1 +

50 kW

R

G

INA128:

INA129:

INA128, INA129

www.ti.com

SBOS051C – OCTOBER 1995 – REVISED OCTOBER 2015

7 Detailed Description

7.1 Overview

The INA12x instrumentation amplifier is a type of differential amplifier that has been outfitted with input protection

circuit and input buffer amplifiers, which eliminate the need for input impedance matching and make the amplifier

particularly suitable for use in measurement and test equipment. Additional characteristics of the INA128 include

a very low DC offset, low drift, low noise, very high open-loop gain, very high common-mode rejection ratio, and

very high input impedances. The INA12x is used where great accuracy and stability of the circuit both short and

long term are required.

7.2 Functional Block Diagram

7.3 Feature Description

The INA12x devices are low power, general-purpose instrumentation amplifiers offering excellent accuracy. The

versatile three-operational-amplifier design and small size make the amplifiers ideal for a wide range of

applications. Current-feedback input circuitry provides wide bandwidth, even at high gain. A single external

resistor sets any gain from 1 to 10,000. The INA128 is laser trimmed for very low offset voltage (25

μV typical)

and high common-mode rejection (93 dB at G

≥ 100). These devices operate with power supplies as low as

±2.25 V, and quiescent current of 2 mA, typically. The internal input protection can withstand up to ±40 V without

damage.

7.4 Device Functional Modes

7.4.1 Noise Performance

measured from 0.1 to 10 Hz (G

≥ 100). This provides dramatically improved noise when compared to state-of-

the-art chopper-stabilized amplifiers.

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Product Folder Links: INA128 INA129