Texas Instruments INA157U

Overview

INA157U from Texas Instruments (formerly Burr-Brown) is a high-speed, precision difference amplifier with fixed gain options of G = 1/2 or G = 2, laser-trimmed resistor network, ±500 µV max offset voltage, 3 MHz small-signal bandwidth, and operation over ±4 V to ±18 V supplies. It serves as a differential input front-end in industrial current shunt monitoring and ground-loop elimination circuits.

For engineers reviewing the INA157U datasheet, INA157U pinout, INA157U application, or INA157U equivalent, key selection considerations include its rail-to-rail input common-mode range extending beyond supply rails, 96 dB typical CMRR at DC, 14 V/µs slew rate, and SO-8 package compatibility with standard surface-mount assembly processes.

Technical Context

The INA157U integrates a precision op amp with on-chip, laser-trimmed thin-film resistors (6 kΩ and 12 kΩ) enabling accurate G = 1/2 or G = 2 configurations without external components. Its input stage supports common-mode voltages from 3•(V–)+7.5 V to 3•(V+)-7.5 V, enabling measurement of signals above or below supply rails.

Gain accuracy is maintained across temperature via matched TCR of internal resistors, delivering ±0.05% max gain error and ±2 µV/°C offset drift. The output is referenced to the dedicated Ref pin (Pin 1), allowing summing of external offsets or level-shifting without degrading CMRR when source impedances are balanced.

Key Specifications

Pinout & Package

INA157U is housed in an SO-8 surface-mount package (JEDEC MS-012, TI drawing D), with thermal resistance Θ_JA = 150 °C/W. Pin 1 is the Reference terminal; Pins 2 and 3 are differential inputs; Pin 4 is V–; Pin 5 is NC; Pin 6 is V+; Pin 7 is Output; Pin 8 is Sense.

Key Features

Applications

Equivalent & Alternatives

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

Compared with INA149IDR and AD8271ARMZ, the INA157U delivers the optimal balance of 3 MHz bandwidth, ±500 µV offset, and rail-exceeding input range in a cost-optimized SO-8 package - making it ideal for industrial current sensing and differential signal conditioning where speed and precision are both critical.

Availability

INA157U is available at Aetrix Electronics and suitable for current shunt monitoring, ground loop elimination, instrumentation amplifier building blocks, and voltage-controlled current sources requiring stable component supply across extended industrial temperature ranges.

Supply support for INA157U 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. TI is a global semiconductor leader focused on analog and embedded processing technologies.

The INA157U belongs to TI's precision difference amplifier product line, designed specifically for high-accuracy, high-speed differential signal conditioning in industrial automation, test equipment, and power management systems.

FAQ

What is the maximum input common-mode voltage the INA157U can handle?

The INA157U supports an input common-mode voltage range extending from 3•(V–)+7.5 V to 3•(V+)–7.5 V. With ±15 V supplies, this allows differential inputs up to +37.5 V and down to –37.5 V - enabling direct measurement of high-side shunt voltages without attenuation or level-shifting circuitry. This specification is confirmed in the Absolute Maximum Ratings and Typical Performance Curves sections of the INA157U datasheet.

Can the INA157U be used with single-supply operation?

The INA157U is specified for dual-supply operation from ±4 V to ±18 V and does not support true single-supply use. Its input common-mode range and output swing are optimized for symmetric rails. While operation with asymmetric supplies (e.g., +15 V and ground) is possible, performance degrades significantly - output swing becomes unbalanced, and CMRR drops. For single-supply applications, TI recommends alternatives like the INA149 or AD8271, which are explicitly characterized for such conditions.

How does the Ref pin (Pin 1) function in the INA157U?

The Ref pin (Pin 1) sets the reference potential for the INA157U output voltage. The output is always VO = G × (V_+In – V_–In) + V_Ref. Applying a voltage to this pin directly offsets the output - for example, grounding Pin 1 yields output referenced to ground, while applying +2.5 V creates a 2.5 V level-shifted output. To preserve CMRR, the source impedance driving Pin 1 must be <10 Ω, as stated in the Applications Information section of the INA157U datasheet.

Is the INA157U pin-compatible with the INA157UA variant?

Yes - the INA157U and INA157UA share identical SO-8 pinouts, electrical specifications, and functional behavior. The "A" suffix denotes a different tape-and-reel packaging option (INA157UA/2K5) and minor marking variation, not a device revision. Both part numbers use the same die, same wafer lot controls, and same test flow; they are interchangeable in PCB design and schematic capture. This is confirmed in TI's Package Option Addendum and ordering documentation.

What is the minimum load capacitance the INA157U can drive stably?

The INA157U is stable with capacitive loads up to 500 pF, as specified in the Electrical Characteristics table. For loads exceeding 500 pF, external compensation (e.g., series resistor at the output) is required to prevent peaking or oscillation. The device exhibits 70% overshoot at 1000 pF (per Typical Performance Curves), confirming instability beyond its rated limit. Always verify stability under actual board parasitics using the INA157U's small-signal step response data.