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-HT, INA129-HT

SBOS501F – JANUARY 2010 – REVISED FEBRUARY 2015

www.ti.com

8 Detailed Description

8.1 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 INA12x 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.

8.2 Functional Block Diagram

8.3 Feature Description

The INA128-HT and INA129-HT 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-HT and INA129-HT are 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.

14

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