Texas Instruments INA128HD

Overview

INA128HD from Texas Instruments is a high-temperature precision instrumentation amplifier in an 8-pin SOIC package, featuring laser-trimmed 25 µV typical offset voltage, 95 dB typical CMR at G ≥100, ±40 V input overvoltage protection, and operation from ±2.25 V to ±18 V supplies. It delivers stable performance in downhole oil/gas sensing and aerospace engine monitoring where extreme thermal reliability is required.

For engineers reviewing the INA128HD datasheet, INA128HD pinout, INA128HD application, or INA128HD equivalent, this page provides verified specifications, validated pin functions, confirmed high-temperature operating limits (–55°C to +175°C), and real-world design implications for bridge, thermocouple, and RTD signal conditioning circuits.

Technical Context

The INA128HD uses a three-op-amp architecture with current-feedback input stages enabling 1.3 MHz bandwidth at G = 1 and 20 kHz at G = 1000. Its gain is set by a single external resistor RG using the equation G = 1 + 50 kΩ/RG, with internal 50 kΩ metal-film resistors laser-trimmed for accuracy and low drift.

Input stage overvoltage protection clamps to ±40 V without damage, and the reference (Ref) pin enables output level shifting. The device is specified for continuous operation up to +175°C junction temperature with 110°C/W junction-to-ambient thermal resistance in SOIC-8 packaging.

Key Specifications

Pinout & Package

INA128HD is housed in an 8-pin SOIC (D) package measuring 4.90 mm × 3.91 mm, optimized for surface-mount assembly and thermal dissipation in high-reliability PCBs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with INA129HT and AD8421ARZ, the INA128HD uniquely balances programmable gain, extreme-temperature operation up to +175°C, and superior CMR at high gains-making it optimal for downhole, aerospace, and industrial systems requiring both flexibility and ruggedness.

Availability

INA128HD is available at Aetrix Electronics and suitable for downhole sensing, aerospace engine monitoring, and industrial RTD signal conditioning requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for INA128HD 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 expertise in high-reliability signal conditioning ICs.

The INA12x-HT product line was engineered specifically for extreme-temperature applications-including oil/gas exploration, aerospace propulsion, and geothermal energy systems-where conventional amplifiers fail due to thermal drift or parametric shift.

FAQ

What is the maximum operating temperature for INA128HD?

The INA128HD is fully specified for continuous operation from –55°C to +175°C ambient temperature, with life derating data provided in Figure 1 of the SBOS501F datasheet. Its SOIC-8 package achieves 110°C/W junction-to-ambient thermal resistance, enabling reliable use in downhole tools and jet engine control units where thermal management is constrained.

How does the gain-setting resistor RG affect accuracy in INA128HD?

In the INA128HD, gain is calculated as G = 1 + 50 kΩ/RG, where the 50 kΩ term consists of laser-trimmed on-die resistors. External RG contributes directly to gain error-e.g., a 1% tolerance RG introduces ~1% gain uncertainty. For G = 100, use RG = 505 Ω (1% standard value); for G = 1000, use RG = 50.5 Ω, accounting for PCB trace resistance at low values.

Can INA128HD interface directly with single-supply systems?

Yes-the INA128HD supports single-supply operation when the Ref pin is biased to mid-rail (e.g., V+/2) and input common-mode voltage remains within (V−)+1.7 V to (V+)-1.4 V. Output swings to within 1.4 V of each rail at 10 kΩ load, so with V+ = 5 V and V− = 0 V, VO delivers 0.8 V to 4.2 V for G = 1, preserving headroom for ADC interfacing.

What protection features does INA128HD include against input overvoltage?

The INA128HD integrates internal overvoltage protection circuitry that withstands ±40 V applied continuously to either input pin without damage or parametric shift. This eliminates external series resistors in 24 V industrial fieldbus interfaces and protects against ESD events up to ±2000 V HBM, as verified in Section 7.2 of SBOS501F.

Is INA128HD pin-compatible with other members of the INA12x-HT family?

Yes-the INA128HD shares identical pinout and package (SOIC-8) with INA128-HT and INA129-HT variants. Pin functions-RG (1,8), V–IN (2), V+IN (3), V– (4), Ref (5), VO (6), V+ (7)-are electrically and mechanically identical. However, gain equations differ: INA128HD uses G = 1 + 50 kΩ/RG, while INA129HT uses G = 1 + 49.4 kΩ/RG, requiring RG value adjustment for same gain.