Texas Instruments INA155U

Overview

INA155U from Texas Instruments (formerly Burr-Brown) is a single-supply, rail-to-rail output CMOS instrumentation amplifier optimized for low-voltage sensor signal conditioning. It delivers fixed gains of 10 V/V or 50 V/V via pin strapping, ±200 µV max input offset voltage, 550 kHz bandwidth at G = 10, and operates from +2.7 V to +5.5 V across –55°C to +125°C - enabling precision bridge and thermocouple amplification in industrial sensor modules.

For engineers reviewing the INA155U datasheet, INA155U pinout, INA155U application, or INA155U equivalent, key selection criteria include its rail-to-rail output swing within 10 mV of rails, ultra-low 0.2 pA input bias current, internal gain configuration (no external resistors required for G = 10/50), guaranteed performance over extended temperature, and SO-8 package compatibility with standard PCB layouts.

Technical Context

The INA155U implements a three-op-amp architecture with complementary CMOS input stages, enabling rail-to-rail common-mode input operation outside the (V+) – 1.8 V to (V+) – 0.8 V transition zone. Its internal gain-setting network eliminates external resistor matching requirements for G = 10 (pins 1 & 8 open) or G = 50 (pins 1 & 8 shorted).

Output stage uses class AB common-source transistors to achieve <10 mV rail-to-rail swing into 10 kΩ loads, while maintaining 6.5 V/µs slew rate and 5 µs 0.1% settling time at G = 10. Input protection includes ESD diodes clamping to rails, with safe input range of (V–) – 0.5 V to (V+) + 0.5 V.

Key Specifications

Pinout & Package

INA155U is housed in an 8-pin SOIC (SO-8, package drawing D), surface-mount package with standard 1.27 mm pitch and JEDEC MS-012 outline. Thermal resistance θ_JA = 150°C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with INA155U, INA126UA trades bandwidth and input bias for lower 1/f noise, while AD8221ARMZ offers superior DC precision at the cost of design complexity and absence of pin-strappable gain - making INA155U optimal for cost-sensitive, single-supply, fixed-gain sensor front-ends.

Availability

INA155U is available at Aetrix Electronics and suitable for industrial sensor amplifiers, medical ECG front-ends, and A/D converter driving applications requiring stable component supply, extended temperature qualification, and SO-8 footprint compatibility.

Supply support for INA155U 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 acquired Burr-Brown in 2000 and maintains its precision analog portfolio, emphasizing high-performance signal chain components for industrial, medical, and test equipment markets.

The INA155U belongs to TI's instrumentation amplifier product line, designed specifically for low-voltage, single-supply sensor signal conditioning where rail-to-rail output, low offset, and fixed-gain simplicity are critical.

FAQ

What gain options does the INA155U support, and how are they configured?

The INA155U supports two fixed gains: 10 V/V and 50 V/V. Gain is selected by pin strapping - leaving Pins 1 and 8 open configures G = 10, while shorting them together sets G = 50. No external resistors are required for these standard gains. The INA155U datasheet confirms this configuration is internally trimmed for <0.1% gain error at G = 10 and <0.25% at G = 50 across temperature.

Can the INA155U operate from a single 3.3 V supply, and what is its output swing capability?

Yes, the INA155U is fully specified from +2.7 V to +5.5 V, making it compatible with standard 3.3 V rails. At G = 10 and RL = 10 kΩ, its rail-to-rail output swings within 5–10 mV of both supply rails at +25°C, and within 10 mV over the full –55°C to +125°C range. This allows >3.28 Vpp output swing on a 3.3 V supply, maximizing dynamic range for ADC interfacing.

How does the INA155U handle input bias current, and what external components are required?

The INA155U features CMOS inputs with 0.2 pA typical input bias current. A low-impedance return path must be provided for both inputs - e.g., matched resistors to Ref or V– - to prevent saturation. The INA155U datasheet specifies that floating inputs will exceed common-mode range and cause invalid output. No external compensation is needed for basic operation, but bias paths are mandatory.

Is the INA155U pin-compatible with other instrumentation amplifiers in SO-8 packages?

No, the INA155U has a unique pinout optimized for its internal gain configuration (Pins 1 & 8 as RG terminals). It is not pin-compatible with industry-standard SO-8 instrumentation amplifiers like the AD620 or INA128. Layout reuse requires verification against the INA155U pin diagram - particularly the placement of V+, V–, Ref, and RG pins - to avoid functional failure.

What is the maximum common-mode input voltage range for the INA155U at 5.5 V supply and G = 10?

At VS = +5.5 V and G = 10, the INA155U supports a common-mode input range of 0.3 V to 5.2 V, as specified in the datasheet. Operation above (V+) – 1.8 V (i.e., >3.7 V) reduces CMRR; the INA155U datasheet recommends keeping VCM below 3.7 V or above 4.7 V for best performance. This range accommodates bridge outputs centered at VS/2 (2.75 V) with ample margin.