Texas Instruments INA133U

Overview

INA133U from Texas Instruments (originally Burr-Brown) is a precision unity-gain difference amplifier IC designed for high-accuracy differential signal conditioning. It features ±450 µV max input offset voltage, 1.5 MHz bandwidth, 5 V/µs slew rate, and operates from ±2.25 V to ±18 V dual supplies. It serves as a building block in battery-powered instrumentation, automotive sensor interfaces, and industrial current/differential line receivers.

For engineers reviewing the INA133U datasheet, INA133U pinout, INA133U application, or INA133U equivalent, key selection considerations include its laser-trimmed resistor network enabling 90 dB CMRR, rail-to-rail input common-mode range extending beyond supply rails (2×V₊ – 3 V to 2×V_– + 3 V), low 950 µA quiescent current, and SO-8 surface-mount package compatibility with space-constrained PCB layouts.

Technical Context

The INA133U integrates a precision op amp with on-chip 25 kΩ laser-trimmed thin-film resistors configured as a fixed-gain = 1 difference amplifier. Its resistor ratio matching ensures stable gain accuracy and common-mode rejection over temperature, with TCR tracking limiting gain drift to ±1 ppm/°C and offset drift to ±5 µV/°C max.

It supports both dual-supply (±2.25 V to ±18 V) and single-supply (+4.5 V to +36 V) operation, with input common-mode voltage range exceeding supply rails - enabling direct measurement of signals referenced to ground or floating sources without level-shifting circuitry. Output swing is specified to within 1.5 V of each rail at 10 kΩ load.

Key Specifications

Pinout & Package

INA133U is housed in an SO-8 surface-mount package (Package Drawing D, JEDEC MS-012), with thermal resistance θ_JA = 150°C/W. Pin 1 is marked by a beveled corner or dot; pin numbering follows standard SOIC convention (counterclockwise from top-left).

Key Features

Applications

Equivalent & Alternatives

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

Compared with INA132UA and AD8271ARMZ, the INA133U delivers the best balance of ultra-low quiescent current (0.95 mA), high DC CMRR (90 dB), and rail-exceeding input range - making it optimal for cost-sensitive, noise-immune, battery-operated differential measurement systems where speed up to 1.5 MHz suffices.

Availability

INA133U is available at Aetrix Electronics and suitable for current sensing in motor drives, precision bipolar signal conditioning, battery management system monitoring, and automotive differential line receivers requiring stable component supply across industrial temperature ranges (–40°C to +85°C).

Supply support for INA133U 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 (TI) is a global semiconductor leader delivering analog and embedded processing solutions, with heritage from Burr-Brown's precision analog expertise acquired in 2000.

The INA133U belongs to TI's precision difference amplifier product line, engineered specifically for high-accuracy, low-cost differential signal acquisition in industrial, automotive, and portable instrumentation where laser-trimmed resistor networks ensure stable gain and CMRR without external calibration.

FAQ

What is the maximum capacitive load the INA133U can drive while remaining stable?

The INA133U is specified for stable operation with capacitive loads up to 1000 pF. Driving larger loads may cause peaking or oscillation; for loads >1000 pF, a series resistor (typically 10–50 Ω) between the output and load is recommended to maintain phase margin. This limit is verified per the manufacturer's typical performance curves and applies across the full operating temperature range of –40°C to +85°C for the INA133U.

Can the INA133U operate from a single +5 V supply?

Yes, the INA133U supports single-supply operation from +4.5 V to +36 V. When powered from +5 V, the input common-mode range extends from –2 V to +7 V (2×V₊ – 3 V to 2×V_– + 3 V, with V_– = 0 V), and output swings from ~0.8 V to ~3.7 V at 10 kΩ load. Full specifications are guaranteed at +5 V per the datasheet's VS = ±5 V test conditions, confirming reliable operation in 5 V microcontroller-based systems.

What is the function of the Sense pin (Pin 8) on the INA133U?

The Sense pin (Pin 8) on the INA133U is an internal connection point to the laser-trimmed resistor network and is not intended for external use. It must remain unconnected - no trace, pad, or component should be attached. Connecting or loading this pin disrupts the precision resistor ratio, degrading gain accuracy and CMRR. The INA133U datasheet explicitly states "Sense" as an internal node, and all functional operation is defined solely by Pins 1–7.

How does the Ref pin (Pin 1) affect the output of the INA133U?

The Ref pin (Pin 1) on the INA133U sets the output reference level: V_OUT = (V_+In – V_–In) + V_REF. When grounded, output is centered at 0 V. Applying a voltage (e.g., +2.5 V) shifts the entire output range accordingly. To preserve CMRR, the source impedance driving Ref must be <10 Ω; higher impedances degrade common-mode rejection. This feature enables offset nulling, level-shifting, and bipolar-to-unipolar conversion in the INA133U.

Is the INA133U RoHS compliant and lead-free?

Yes, the INA133U is RoHS compliant and classified as "Green (RoHS & no Sb/Br)" per TI's packaging documentation. It uses CU NIPDAU lead finish and meets JEDEC MSL Level-3 moisture sensitivity standards (260°C peak reflow, 168-hour floor life). The "U" suffix denotes the standard SOIC package variant qualified for industrial temperature range (–40°C to +85°C) and fully compliant with EU RoHS Directive 2011/65/EU and related restrictions on brominated flame retardants and antimony.