Texas Instruments INA128U

Overview

INA128U from Texas Instruments is a precision, low-power instrumentation amplifier designed for high-accuracy differential signal conditioning in noisy industrial and medical environments. It delivers 50μV maximum offset voltage, 120dB minimum CMRR at G=100, 1.3MHz bandwidth (G=1), ±40V input overvoltage protection, and operates from ±2.25V to ±18V supplies - enabling use in pressure transmitters, ECG front-ends, and weigh-scale analog input modules.

For engineers reviewing the INA128U datasheet, INA128U pinout, INA128U application, or INA128U equivalent, key selection criteria include its laser-trimmed gain accuracy (±0.024% at G=1), low 700μA quiescent current, SOIC-8 package compatibility, and industry-standard gain equation (G = 1 + 50kΩ/R_G) requiring only one external resistor.

Technical Context

The INA128U implements a three-op-amp architecture with current-feedback input stages, enabling stable 200kHz bandwidth even at G=100. Its input stage includes integrated overvoltage protection diodes and high-impedance buffers (10GΩ || 2pF differential, 100GΩ || 9pF common-mode), eliminating need for external input impedance matching.

Gain is set externally via resistor R_G between pins 1 and 8, supporting programmable gains from 1 to 10,000. The device uses laser trimming for initial offset (±50μV max) and CMRR (≥120dB at G=100), with thermal drift limited to ±0.5μV/°C and long-term stability of ±0.1μV/mo.

Key Specifications

Pinout & Package

INA128U is supplied in an 8-pin SOIC (D) package measuring 4.9mm × 6mm, optimized for surface-mount assembly and thermal performance (R_θJA = 110°C/W).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar instrumentation amplifier applications.

Compared with INA128PA, the INA128U trades initial precision for cost and availability; compared with INA828, it retains identical gain architecture and supply flexibility while accepting higher bias current for broader legacy design compatibility.

Availability

INA128U is available at Aetrix Electronics and suitable for pressure transmitter design, ECG front-end development, and industrial analog input module production requiring stable component supply and long-term manufacturability.

Supply support for INA128U includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor leader specializing in analog and embedded processing technologies, with decades of heritage in precision signal chain components.

The INA12x product line was engineered specifically for high-accuracy industrial measurement and medical sensing, emphasizing robustness against ESD, wide supply flexibility, and ease of gain configuration in space-constrained layouts.

FAQ

What is the maximum gain achievable with the INA128U, and how is it set?

The INA128U supports gains from 1 to 10,000, set by a single external resistor R_G connected between pins 1 and 8 using the equation G = 1 + 50kΩ/R_G. For G=10,000, R_G = 5Ω is required; however, layout parasitics and resistor tolerance limit practical maximum to ~5,000. The INA128U datasheet provides standard 1% resistor values for common gains in Table 8-1.

Does the INA128U require external input protection when used with industrial sensors?

No - the INA128U integrates robust ±40V input overvoltage protection on both VIN+ and VIN– pins, verified per Figure 6-16 and 6-17 of the datasheet. This eliminates need for external TVS diodes or series current-limiting resistors in typical 24V industrial sensor interfaces, reducing component count and board area.

How does the REF pin affect output behavior in the INA128U?

The REF pin sets the DC level of the INA128U output: V_O = G × (V_IN+ – V_IN–) + V_REF. Connecting REF to ground yields output centered at 0V; connecting to a DAC or bias voltage enables level-shifting. Impedance on REF must be <8Ω to maintain ≥120dB CMRR - use a low-impedance buffer if driving from high-Z sources.

What is the temperature range specification for the INA128U?

The INA128U is specified for operation from –40°C to +85°C ambient temperature, with electrical characteristics guaranteed across this range per Section 6.3 of the datasheet. Junction temperature must not exceed 150°C; thermal resistance R_θJA = 110°C/W (SOIC-8) requires appropriate PCB copper area for high-temperature deployments.

Can the INA128U operate from a single 5V supply?

Yes - the INA128U supports single-supply operation from 4.5V to 36V. At 5V, the input common-mode range is approximately 2V to 3V (V_– + 2 to V₊ – 2), and output swing is typically 0.15V to 4.85V (CSO: FRE). For rail-to-rail output, use the REF pin to bias output mid-supply and ensure input signals stay within linear range.