A precision instrumentation amplifier in SOIC-8, for pulling a small differential signal out of a noisy environment. One external resistor across the two RG pins sets the gain anywhere from 1 to 10000 (G = 1 + 50k/RG), and the three-op-amp topology gives very high common-mode rejection so shared noise on both inputs cancels. Low offset voltage and drift make it the front end for bridge sensors (load cells, pressure), thermocouples, current-shunt sensing, and biopotential measurement. A REF pin sets the output's ground reference. Runs on split supplies from plus/minus 2.25 to plus/minus 18 V.

Pinout

Pin	Name	Type	Function
1	RG	passive	Gain-setting pin. For gains greater than 1, place a gain resistor between pin 1 and pin 8. Gain is set as G = 1 + 50kΩ/RG. Leave open for G = 1.
2	VIN-	input	Inverting (negative) analog input of the instrumentation amplifier. Input common-mode voltage range is (V-)+2V to (V+)-2V; safe input voltage is ±40V with RS = 0Ω.
3	VIN+	input	Non-inverting (positive) analog input of the instrumentation amplifier. Input common-mode voltage range is (V-)+2V to (V+)-2V; safe input voltage is ±40V with RS = 0Ω.
4	V-	power_in	Negative supply rail. Dual-supply range ±2.25V to ±18V; single-supply operation V+ = 4.5V to 36V with V- = 0V. Decouple locally to ground.
5	REF	input	Reference input that sets the output DC reference level. Must be driven by a low-impedance source or connected directly to ground; any source impedance here directly degrades CMRR.
6	VO	output	Amplifier output. VO = G × (VIN+ - VIN-) + VREF, where G = 1 + 50kΩ/RG. Short-circuit protected to VS/2 continuously.
7	V+	power_in	Positive supply rail. Dual-supply range ±2.25V to ±18V; single-supply 4.5V to 36V with V- = 0V. Decouple locally with a 0.1µF ceramic capacitor.
8	RG	passive	Gain-setting pin. For gains greater than 1, place a gain resistor between pin 1 and pin 8. Gain is set as G = 1 + 50kΩ/RG. Leave open for G = 1.

Key specifications

Parameter	Value
Type	Instrumentation amplifier
Gain	1 to 10000 (G = 1 + 50k/RG)
Gain set	single external resistor (RG)
CMRR	120 dB at G=100
Offset voltage	50 µV max
Supply	±2.25 to ±18 V
Quiescent current	~700 µA
Package	SOIC-8

Ordering variants

Same part, different packaging or reel option.

INA128UA (SOIC-8)
INA128U (SOIC-8, tape & reel)

CAD (KiCad official)

Symbol: Amplifier_Instrumentation:INA128
Footprint: Package_SO:SOIC-8_3.9x4.9mm_P1.27mm
3D model: SOIC-8 (KiCad packages3D)

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

Datasheet: Texas Instruments datasheet (42 pp, sha256 1b13f3f996838202, retrieved 2026-08-17, tier: manufacturer)
Extractor: ds2sf (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF