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Texas Instruments INA121UA/2K5
- Part No.:
- INA121UA/2K5
- Manufacturer:
- Texas Instruments
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
INA121UA/2K5.pdf
- Description:
- IC INST AMP 1 CIRCUIT 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,435
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Product details
Overview
INA121UA/2K5 from Texas Instruments (formerly Burr-Brown) is a FET-input, low-power instrumentation amplifier optimized for high-impedance sensor interfaces. It delivers ±4pA bias current, ±200µV input offset voltage, 106dB CMR at G=100, and operates from ±2.25V to ±18V supplies - enabling precision signal conditioning in battery-powered ECG, bridge transducer, and portable data acquisition systems.
For engineers reviewing the INA121UA/2K5 datasheet, INA121UA/2K5 pinout, INA121UA/2K5 application, or INA121UA/2K5 equivalent, key selection criteria include its laser-trimmed gain accuracy (±0.05% at G=100), 50kHz bandwidth at G=100, SOIC-8 package compatibility with automated assembly, and validated performance across –40°C to +85°C industrial temperature range.
Technical Context
The INA121UA/2K5 implements a three-op-amp architecture with internal 40kΩ feedback resistors and laser-trimmed metal-film elements, enabling precise gain setting via a single external resistor (RG) from 1V/V to 10,000V/V. Its current-feedback topology sustains 50kHz bandwidth even at G=100 while consuming only ±450µA quiescent current.
Input overvoltage protection withstands ±40V on VIN+ and VIN– terminals without damage. The Ref pin establishes output reference level and requires low-impedance grounding (<8Ω) to maintain >100dB CMR; internal input impedance exceeds 10¹²Ω || 1pF differential and 10¹²Ω || 12pF common-mode.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Bias Current | ±4pA - enables direct interfacing with >1MΩ source impedances (e.g., piezoelectric sensors, dry electrodes) without significant offset error. |
| Input Offset Voltage | ±200µV - laser-trimmed for <0.001% nonlinearity error at G=1, critical for DC-coupled physiological amplifiers. |
| CMR @ G=100 | 106dB - rejects 99.9997% of 60Hz common-mode interference in ECG/EMG front-ends when Ref is properly grounded. |
| Gain Bandwidth | 50kHz @ G=100 - supports fast-sampling multi-channel DAQ systems with ≤20µs settling time to 0.01%. |
| Supply Range | ±2.25V to ±18V - allows operation from single 5V rails (±2.5V) or dual ±15V lab supplies without performance degradation. |
| Quiescent Current | ±450µA - enables >100-hour battery life in portable instrumentation with minimal thermal drift. |
| Input Protection | ±40V absolute max - eliminates need for external clamping diodes in industrial transducer interfaces exposed to ESD or load dump. |
Pinout & Package
INA121UA/2K5 is housed in an 8-pin SOIC (SO-8) surface-mount package per JEDEC MS-012, variation AA, with 1.27mm pitch, 3.9mm width, and 1.75mm max height. Thermal resistance θJA = 150°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | RG (Gain Set) | Connects to Pin 8 to set gain per G = 1 + 50kΩ/RG; low-value RG (e.g., 511Ω for G=100) requires short PCB traces to avoid wiring-resistance errors. |
| 2 | VIN– | Inverting input; must be routed adjacent to Pin 3 with matched trace length/impedance to preserve CMR above 1kHz. |
| 3 | VIN+ | Non-inverting input; forms balanced differential pair with Pin 2; bias current return path required via external resistors. |
| 4 | V– | Negative supply rail; decouple with 0.1µF ceramic capacitor placed ≤2mm from Pin 4 to suppress PSRR degradation. |
| 5 | Ref | Output reference node; must connect to low-impedance ground (≤8Ω) to maintain >100dB CMR; buffered voltage sources acceptable. |
| 6 | VO | Amplified output; drives loads ≥10kΩ directly; capacitive loads >1000pF require series isolation resistor to prevent oscillation. |
| 7 | V+ | Positive supply rail; decouple with 0.1µF ceramic capacitor placed ≤2mm from Pin 7 to ensure stable operation at full bandwidth. |
| 8 | RG (Gain Set) | Completes gain-setting resistor loop with Pin 1; unused pins must remain unconnected - no NC functionality. |
Key Features
| Feature | Design Value |
|---|---|
| FET-input architecture | Enables ±4pA bias current for accurate amplification of signals from high-Z sources like RTDs, thermocouples, and capacitive sensors without loading error. |
| Laser-trimmed internal resistors | Guarantees ±0.05% gain error at G=100 and ±25ppm/°C gain drift, eliminating need for external calibration in production test fixtures. |
| Integrated overvoltage protection | Withstands ±40V input faults without latch-up or parameter shift, reducing BOM count and board space in industrial field I/O modules. |
| Low-noise design | 20nV/√Hz input-referred noise at 1kHz (G=100) ensures <1µVp-p integrated noise in 0.1–10Hz biomedical bands, meeting IEC 60601 ECG requirements. |
| Wide supply flexibility | Operates from ±2.25V (4.5V total) to ±18V, supporting both coin-cell-powered wearables and benchtop test equipment with identical layout. |
Applications
| ECG Monitoring System | Strain Gauge Bridge Interface |
|---|---|
|
Use Scenario: Amplifying microvolt-level cardiac signals from dry Ag/AgCl electrodes in ambulatory heart rate monitors. IC Role / Device Role / Timing Role: Primary front-end instrumentation amplifier providing programmable gain (G=100–500), high CMR, and ultra-low input current to prevent electrode polarization. Use Value: ±4pA bias current prevents DC drift during long-term monitoring; 106dB CMR rejects 60Hz power-line interference without active guarding. |
Use Scenario: Conditioning mV-level differential outputs from 350Ω Wheatstone bridges in structural health monitoring sensors. IC Role / Device Role / Timing Role: Precision bridge amplifier with gain set by 511Ω resistor (G=100), referenced to stable system ground via low-impedance Ref connection. Use Value: ±200µV offset voltage ensures <0.1% full-scale error at 10mV bridge output; ±40V input protection tolerates cable ESD events in factory environments. |
| Portable Gas Sensor Signal Chain | Multi-Channel Biopotential Acquisition |
|
Use Scenario: Amplifying nanoamp-level currents from electrochemical gas sensors using transimpedance configuration with external feedback. IC Role / Device Role / Timing Role: Low-noise, low-drift amplifier stage converting sensor current to voltage prior to ADC sampling at 1ksps. Use Value: 20nV/√Hz noise floor preserves signal integrity in 0.1–100Hz gas concentration bands; ±450µA quiescent current extends AA-battery life to >12 months. |
Use Scenario: Simultaneous acquisition of EEG, EMG, and EOG signals in clinical neurodiagnostic equipment with 16-channel analog front-end. IC Role / Device Role / Timing Role: Channelized instrumentation amplifier per input, configured for G=1000 with 50Ω RG to achieve 5kHz bandwidth per channel. Use Value: 5µs overload recovery prevents inter-channel crosstalk during transient events; SOIC-8 package enables dense 0.5mm-pitch routing on 4-layer PCBs. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar instrumentation amplifier applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| INA128UA/2K5 | Higher CMR (120dB @ G=100), lower offset drift (±0.1µV/°C), but higher quiescent current (±1.5mA). | Better suited for laboratory-grade precision measurements where power is not constrained. | Select INA128UA/2K5 when CMR >115dB is required and ±1.5mA supply current is acceptable. |
| AD8421ARMZ | Lower input noise (7nV/√Hz), wider bandwidth (10MHz @ G=1), but higher bias current (±1nA) and no integrated overvoltage protection. | Preferred for high-frequency sensor interfaces (e.g., ultrasonic NDT) requiring >1MHz bandwidth. | Choose AD8421ARMZ for AC-coupled, high-bandwidth applications where external protection can be added. |
Compared with INA121UA/2K5, INA128UA/2K5 trades 3× higher supply current for 14dB CMR improvement and 5× lower drift, while AD8421ARMZ sacrifices input protection and bias current performance for 200× higher bandwidth - making INA121UA/2K5 optimal for cost-sensitive, low-power, high-impedance DC/low-frequency sensing.
Availability
INA121UA/2K5 is available at Aetrix Electronics and suitable for ECG monitoring systems, strain gauge bridge interfaces, portable gas sensor signal chains, and multi-channel biopotential acquisition requiring stable component supply across industrial temperature ranges and long-lifecycle production programs.
Supply support for INA121UA/2K5 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, renowned for high-accuracy data converters, op amps, and instrumentation amplifiers used in medical, industrial, and test equipment.
The INA121 series was designed specifically for low-power, high-impedance sensor signal conditioning in portable and battery-operated instrumentation - emphasizing laser-trimmed DC accuracy, robust input protection, and SOIC-8 manufacturability.
FAQ
What is the maximum gain achievable with INA121UA/2K5 and how is it set?
The INA121UA/2K5 supports gains from 1V/V to 10,000V/V using a single external resistor (RG) between Pins 1 and 8, per the equation G = 1 + 50kΩ/RG. For G=10,000, RG = 5.001Ω is required; however, practical implementation uses 4.99Ω (1% tolerance) with attention to PCB trace resistance. The INA121UA/2K5 datasheet confirms this range under "Gain Range" in the specifications table.
Does INA121UA/2K5 require external components for basic operation?
Yes - the INA121UA/2K5 requires at minimum: (1) a gain-setting resistor (RG) between Pins 1 and 8, (2) 0.1µF decoupling capacitors on V+ (Pin 7) and V– (Pin 4), and (3) a low-impedance connection (<8Ω) from Ref (Pin 5) to system ground. These are mandatory per the "Basic Connections" diagram in the INA121UA/2K5 datasheet to ensure specified CMR and stability.
Can INA121UA/2K5 operate from a single 5V supply?
Yes - the INA121UA/2K5 operates from split supplies as low as ±2.25V (total 4.5V), enabling true single-supply use with V+ = 5V and V– = 0V. However, the input common-mode range becomes limited to ~1.2V below V+ and ~2.1V above V–, so VIN+ and VIN– must stay within 0V to 3.8V. This is verified in the "Input Common-Mode Range vs Output Voltage" curve for VS = ±2.5V in the INA121UA/2K5 datasheet.
What is the purpose of the Ref pin on INA121UA/2K5 and how should it be connected?
The Ref pin (Pin 5) sets the output voltage reference level - the output VO equals G × (VIN+ − VIN−) + VREF. It must be connected to a low-impedance node (e.g., clean ground or buffered reference) because >8Ω series resistance degrades CMR to ~80dB. The INA121UA/2K5 application note explicitly warns against unbuffered potentiometers or high-Z sources on Ref, as confirmed in Figure 2 and text on page 9 of the INA121UA/2K5 datasheet.
How does INA121UA/2K5 handle input overvoltage conditions?
The INA121UA/2K5 integrates on-chip overvoltage protection diodes on both inputs, rated for continuous ±40V differential or common-mode input voltage without damage. The "Input Over-Voltage V/I Characteristics" curve (page 5) shows clamping begins at ~±15V, limiting input current to <1mA. This eliminates need for external TVS diodes in most industrial sensor interfaces, a key feature documented in the INA121UA/2K5 Absolute Maximum Ratings table.
INA121UA/2K5 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Amplifier Type:
- Instrumentation
- Number of Circuits:
- 1
- Output Type:
- -
- Slew Rate:
- 0.7V/µs
- Gain Bandwidth Product:
- -
- -3db Bandwidth:
- 5 kHz
- Current - Input Bias:
- 4 pA
- Voltage - Input Offset:
- 300 µV
- Current - Supply:
- 450µA
- Current - Output / Channel:
- 14 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:
- 8-SOIC
INA121UA/2K5 FAQ
1.How can I place an order for INA121UA/2K5 through Aetrix?
Please submit a Request for Quotation (RFQ) for INA121UA/2K5 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 INA121UA/2K5 reliable?
The price and inventory of INA121UA/2K5 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for INA121UA/2K5 is usually 5 days.
3.What payment methods are accepted for INA121UA/2K5?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for INA121UA/2K5 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for INA121UA/2K5?
INA121UA/2K5 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your INA121UA/2K5 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 INA121UA/2K5?
For technical support, including INA121UA/2K5 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your INA121UA/2K5 requirements.
6.How does Aetrix verify that INA121UA/2K5 is sourced from the original manufacturer or authorized distributors?
All INA121UA/2K5 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 INA121UA/2K5 meets industry standards.
7.What is the process for return or replacement of INA121UA/2K5?
All INA121UA/2K5 units undergo pre-shipment inspection (PSI). If there is an issue with INA121UA/2K5, 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 INA121UA/2K5 part is unused and in its original packaging.
Return procedure for INA121UA/2K5:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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