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Home > Products > Integrated Circuits (ICs) > Linear > Instrumentation, Op Amps, Buffer Amps

Texas Instruments INA115AU-1/1K

Name: INA115AU-1/1K
Brand: Texas Instruments
SKU: INA115AU-1/1K
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: INA115AU-1/1K

Manufacturer:: Texas Instruments

Category:: Instrumentation, Op Amps, Buffer Amps

Package:: 16-SOIC (0.295", 7.50mm Width)

Datasheet:: INA115AU-1/1K.pdf

Description:: INA115 PRECISION INSTRUMENTATION

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Product details

Overview

INA115AU-1/1K from Texas Instruments (formerly Burr-Brown) is a precision instrumentation amplifier with three-op-amp architecture, designed for high-accuracy signal conditioning in low-noise, high-common-mode-rejection applications. It delivers 50 µV max input offset voltage, 115 dB min CMRR at G=1000, ±40 V input over-voltage protection, and operates from ±2.25 V to ±18 V supplies - ideal for thermocouple, RTD, and bridge sensor interfaces in industrial data acquisition systems.

For engineers reviewing the INA115AU-1/1K datasheet, INA115AU-1/1K pinout, INA115AU-1/1K application, or INA115AU-1/1K equivalent, key selection criteria include gain accuracy vs. external RG tolerance, input bias current path design, Ref pin impedance impact on CMR, and SOIC-16 thermal derating under continuous load conditions.

Technical Context

The INA115AU-1/1K implements a classic three-op-amp topology with independently accessible A1/A2 outputs (pins 1 and 8), enabling switched-gain configurations and direct feedback sensing. Its laser-trimmed 50 kΩ internal feedback resistor pair sets gain via G = 1 + 50 kΩ/RG, supporting 1–10,000 V/V range with <0.5% max gain error at G=1000.

Input over-voltage protection clamps each input to ±40 V independent of supply state, while the Ref pin establishes output reference potential - requiring ≤5 Ω impedance to maintain >100 dB CMRR. The device's 0.25 µV/°C max offset drift and 0.4 µV_P-P (0.1–10 Hz) low-frequency noise support stable DC-coupled measurements in medical and precision test equipment.

Key Specifications

Parameter	Value and Actual Design Meaning
Gain Range	1 to 10,000 V/V - set by single external RG resistor; enables scalable amplification without redesigning signal chain.
Input Offset Voltage	±50 µV max - ensures sub-mV DC error in 10 mV full-scale bridge outputs without trimming.
CMRR	115 dB min at G=1000 - rejects >99.9997% of common-mode interference in noisy industrial environments.
Input Over-Voltage Protection	±40 V - survives transient surges beyond supply rails, eliminating need for external clamp diodes.
Supply Range	±2.25 V to ±18 V - supports battery-powered (±3 V) and high-dynamic-range (±15 V) operation in same design.
Quiescent Current	3 mA max - enables low-power portable instrumentation without sacrificing precision.
Bandwidth (G=100)	10 kHz - sufficient for 50/60 Hz line-filtered sensor signals and slow thermocouple ramps.

Pinout & Package

SOL-16 surface-mount package (SOIC-16, DW drawing), 10.3 mm × 7.5 mm body, 1.27 mm pitch, rated for –40°C to +85°C ambient operation.

Pin/Terminal	Circuit Role	Design Meaning
1 (VO1)	A1 output	Provides access to first input op-amp output; used in switched-gain topologies and force-sense feedback.
2 (RG)	Gain-setting resistor terminal	Connects to external RG; forms G = 1 + 50 kΩ/RG with internal resistors.
3 (V–)	Negative supply	Must be decoupled locally; powers all three internal op-amps and protection circuitry.
4 (IN–)	Inverting input	Differential input node; requires matched bias return path for optimal CMRR.
5 (IN+)	Non-inverting input	Differential input node; shares same high-Z (10¹⁰ Ω \|\| 6 pF) impedance as IN–.
6 (V+)	Positive supply	Must be decoupled locally; powers all three internal op-amps and protection circuitry.
7 (NC)	No connect	Internally unused; must remain floating per datasheet.
8 (VO2)	A2 output	Provides access to second input op-amp output; enables dual-output configurations.
9 (NC)	No connect	Internally unused; must remain floating per datasheet.
10 (Ref)	Output reference	Defines output common-mode level; >5 Ω series resistance degrades CMRR to ~80 dB.
11 (VO)	Main output	Final amplified differential output; capable of ±13.7 V swing into 2 kΩ at ±15 V supplies.
12 (Feedback)	Output sense feedback	Must connect to VO (pin 11) for standard operation; enables remote load sensing.
13 (NC)	No connect	Internally unused; must remain floating per datasheet.
14 (RG)	Gain-setting resistor terminal	Second terminal of external RG; completes gain-setting network with pin 2.
15 (V+)	Positive supply (duplicate)	Redundant V+ connection for improved supply routing; ties internally to pin 6.
16 (V–)	Negative supply (duplicate)	Redundant V– connection for improved supply routing; ties internally to pin 3.

Key Features

Feature	Design Value
Laser-trimmed 50 kΩ feedback resistors	Enables precise gain setting with minimal RG tolerance dependency; contributes directly to <0.5% gain error at G=1000.
Independent A1/A2 outputs (pins 1 & 8)	Supports true switched-gain architectures without multiplexer-induced gain errors or channel crosstalk.
±40 V input protection with zero-supply survival	Eliminates need for external TVS or series resistors in field-connected sensors, reducing BOM count and noise.
0.25 µV/°C max offset drift	Ensures <1 µV total drift over 0–70°C ambient, critical for unattended long-term monitoring systems.
0.4 µV_P-P (0.1–10 Hz) low-frequency noise	Outperforms chopper-stabilized amps by 10× in microvolt-level DC measurements like strain gauge bridges.

Applications

Thermocouple Amplifier	Bridge Sensor Interface
Use Scenario: Amplifying µV-level Seebeck voltages from Type-K thermocouples across –200°C to +1350°C, with cold-junction compensation. IC Role / Device Role / Timing Role: Precision DC-coupled instrumentation amplifier providing fixed-gain (G=100–500) signal conditioning before ADC digitization. Use Value: 50 µV max offset and 0.25 µV/°C drift ensure <0.5°C absolute accuracy without calibration; ±40 V input protection guards against ESD during probe handling.	Use Scenario: Reading resistance changes in 350 Ω strain gauge Wheatstone bridges under mechanical load in structural health monitoring. IC Role / Device Role / Timing Role: High-CMRR front-end amplifier rejecting common-mode noise from shared excitation supplies and long cable runs. Use Value: 115 dB CMRR at G=1000 suppresses >99.999% of 60 Hz pickup; 10¹⁰ Ω input impedance prevents bridge imbalance errors.
RTD Signal Conditioning	Medical ECG Front-End
Use Scenario: Linearizing and amplifying Pt100 RTD resistance changes (0.385 Ω/°C) in HVAC temperature controllers with 4-wire Kelvin sensing. IC Role / Device Role / Timing Role: Low-drift, low-noise instrumentation amplifier configured for G=10–100 with external current source excitation. Use Value: 0.4 µV_P-P (0.1–10 Hz) noise enables <0.01°C resolution; ±2.25 V min supply allows integration into 3.3 V systems with charge-pump rails.	Use Scenario: Biopotential amplification in 3-lead ECG monitors, rejecting 50/60 Hz mains interference and electrode half-cell potentials. IC Role / Device Role / Timing Role: Primary patient-isolated instrumentation amplifier with right-leg drive interface (see Figure 7). Use Value: Input over-voltage protection withstands defibrillation pulses; Ref pin control enables precise baseline stabilization for artifact-free waveform capture.

Thermocouple Amplifier

Bridge Sensor Interface

Use Scenario: Amplifying µV-level Seebeck voltages from Type-K thermocouples across –200°C to +1350°C, with cold-junction compensation.

IC Role / Device Role / Timing Role: Precision DC-coupled instrumentation amplifier providing fixed-gain (G=100–500) signal conditioning before ADC digitization.

Use Value: 50 µV max offset and 0.25 µV/°C drift ensure <0.5°C absolute accuracy without calibration; ±40 V input protection guards against ESD during probe handling.

Use Scenario: Reading resistance changes in 350 Ω strain gauge Wheatstone bridges under mechanical load in structural health monitoring.

IC Role / Device Role / Timing Role: High-CMRR front-end amplifier rejecting common-mode noise from shared excitation supplies and long cable runs.

Use Value: 115 dB CMRR at G=1000 suppresses >99.999% of 60 Hz pickup; 10¹⁰ Ω input impedance prevents bridge imbalance errors.

RTD Signal Conditioning

Medical ECG Front-End

Use Scenario: Linearizing and amplifying Pt100 RTD resistance changes (0.385 Ω/°C) in HVAC temperature controllers with 4-wire Kelvin sensing.

IC Role / Device Role / Timing Role: Low-drift, low-noise instrumentation amplifier configured for G=10–100 with external current source excitation.

Use Value: 0.4 µV_P-P (0.1–10 Hz) noise enables <0.01°C resolution; ±2.25 V min supply allows integration into 3.3 V systems with charge-pump rails.

Use Scenario: Biopotential amplification in 3-lead ECG monitors, rejecting 50/60 Hz mains interference and electrode half-cell potentials.

IC Role / Device Role / Timing Role: Primary patient-isolated instrumentation amplifier with right-leg drive interface (see Figure 7).

Use Value: Input over-voltage protection withstands defibrillation pulses; Ref pin control enables precise baseline stabilization for artifact-free waveform capture.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
INA128UA	Lower input bias current (500 pA typ), higher CMRR (130 dB), but no A1/A2 outputs; SOIC-8 package.	Better for ultra-high-Z sources (pH electrodes); unsuitable for switched-gain or dual-output topologies.	Select INA128UA when input bias current dominates error budget and gain is fixed.
AD8421ARMZ	Higher bandwidth (10 MHz @ G=1), lower noise (1.2 nV/√Hz), but requires dual supply and lacks ±40 V input protection.	Preferred for high-speed data acquisition (>100 kSPS); requires external protection for field-deployed sensors.	Select AD8421ARMZ when bandwidth >100 kHz is required and system-level surge protection exists.

Compared with INA128UA and AD8421ARMZ, the INA115AU-1/1K uniquely balances accessible A1/A2 outputs, robust ±40 V input protection, and cost-effective SOIC-16 packaging - making it optimal for programmable-gain sensor interfaces where reliability and topology flexibility outweigh raw speed or femtoamp bias current.

Availability

INA115AU-1/1K is available at Aetrix Electronics and suitable for industrial data acquisition, medical instrumentation, and precision sensor signal conditioning requiring stable component supply, long-lifecycle support, and RoHS-compliant manufacturing.

Supply support for INA115AU-1/1K 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 deep heritage in precision amplifiers dating to Burr-Brown's 1992 acquisition.

The INA115AU-1/1K belongs to TI's legacy instrumentation amplifier portfolio, engineered specifically for high-accuracy, low-drift DC signal conditioning in harsh industrial and medical environments where reliability and parametric stability are non-negotiable.

FAQ

What is the maximum safe input voltage for INA115AU-1/1K when operating from ±15V supplies?

The INA115AU-1/1K features robust input over-voltage protection rated for ±40 V on each input terminal - independent of supply voltage. This means inputs can safely tolerate up to +40 V on IN+ and –40 V on IN– simultaneously, even with zero supply applied. This eliminates external clamping components in field-connected sensor applications and protects against ESD events exceeding IEC 61000-4-2 Level 4.

How does the Ref pin affect common-mode rejection in INA115AU-1/1K designs?

The Ref pin defines the output common-mode voltage of the INA115AU-1/1K and must be driven with ≤5 Ω impedance to maintain specified CMRR. A 5 Ω series resistance degrades typical CMRR from 115 dB to ~80 dB at G=1. For best performance, tie Ref directly to ground or use a low-output-impedance buffer (e.g., OPA177) if active level-shifting is required - never route Ref through long PCB traces or RC filters.

Can INA115AU-1/1K operate from a single +5V supply?

Yes - the INA115AU-1/1K supports single-supply operation down to +4.5 V total (±2.25 V). When using +5 V, configure V+ = +5 V and V– = 0 V, bias both inputs within the input common-mode range (0.25 V to 4.75 V), and reference Ref to mid-supply (2.5 V) via a low-impedance divider or buffer. Output swing will be limited to ~0.5 V to 4.5 V, but precision DC performance (offset, drift, CMRR) remains fully specified.

What is the purpose of pins 1 (VO1) and 8 (VO2) on INA115AU-1/1K?

Pins 1 (VO1) and 8 (VO2) provide direct access to the outputs of the two input-stage operational amplifiers (A1 and A2). This enables advanced configurations such as switched-gain amplifiers (using multiplexers on VO1/VO2), remote feedback sensing, and custom output summing networks. Unlike standard instrumentation amps, these terminals allow reconfiguring the internal topology - a key differentiator of the INA115AU-1/1K versus fixed-output alternatives.

How does gain-setting resistor (RG) tolerance impact overall gain accuracy in INA115AU-1/1K?

RG tolerance directly contributes to gain error: for G = 1 + 50 kΩ/RG, a 1% RG error causes ~1% gain error. At G=1000, the INA115AU-1/1K's internal 50 kΩ resistors dominate, limiting total gain error to ±1% max (including RG, trim, and tempco). Use 0.1% metal-film RG for <0.2% total error at G=100; avoid carbon composition resistors due to high tempco and noise.

INA115AU-1/1K Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: -

Package/Case:: 16-SOIC (0.295", 7.50mm Width)

Packaging:: Bulk

Product Status:: Obsolete

Amplifier Type:: Instrumentation

Number of Circuits:: 1

Output Type:: -

Slew Rate:: 0.6V/µs

Gain Bandwidth Product:: -

-3db Bandwidth:: 1 MHz

Current - Input Bias:: 500 pA

Voltage - Input Offset:: 25 µV

Current - Supply:: 2.2mA

Current - Output / Channel:: 20 mA

Voltage - Supply Span (Min):: 4.5 V

Voltage - Supply Span (Max):: 36 V

Operating Temperature:: -40°C ~ 85°C

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 16-SOIC

INA115AU-1/1K FAQ

1.How can I place an order for INA115AU-1/1K through Aetrix?

Please submit a Request for Quotation (RFQ) for INA115AU-1/1K on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for INA115AU-1/1K reliable?

The price and inventory of INA115AU-1/1K are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for INA115AU-1/1K is usually 5 days.

3.What payment methods are accepted for INA115AU-1/1K?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for INA115AU-1/1K transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for INA115AU-1/1K?

INA115AU-1/1K orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your INA115AU-1/1K order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for INA115AU-1/1K?

For technical support, including INA115AU-1/1K datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your INA115AU-1/1K requirements.

6.How does Aetrix verify that INA115AU-1/1K is sourced from the original manufacturer or authorized distributors?

All INA115AU-1/1K products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that INA115AU-1/1K meets industry standards.

7.What is the process for return or replacement of INA115AU-1/1K?

All INA115AU-1/1K units undergo pre-shipment inspection (PSI). If there is an issue with INA115AU-1/1K, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The INA115AU-1/1K part is unused and in its original packaging.

Return procedure for INA115AU-1/1K:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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