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Texas Instruments OPA121KU-TI
- Part No.:
- OPA121KU-TI
- Manufacturer:
- Texas Instruments
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
OPA121KU-TI.pdf
- Description:
- IC OPAMP GP 1 CIRCUIT 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,463
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Product details
Overview
OPA121KU-TI from Texas Instruments is a precision monolithic dielectrically-isolated FET (Difet®) operational amplifier in an 8-pin SOIC package, delivering 6nV/√Hz input voltage noise at 10kHz, ≤5pA max input bias current, and ≤2mV max input offset voltage. It serves as a high-accuracy signal conditioning front-end in low-current, high-impedance sensor interfaces and data acquisition systems.
For engineers reviewing the OPA121KU-TI datasheet, OPA121KU-TI pinout, OPA121KU-TI application, or OPA121KU-TI equivalent, key selection criteria include its ultra-low bias current stability over common-mode voltage, laser-trimmed offset drift of 3µV/°C typ, cascode input architecture for flicker noise reduction, and compatibility with standard 741 pinout-based PCB layouts.
Technical Context
The OPA121KU-TI employs a patented cascode input stage to decouple gate-to-drain voltage variations, enabling stable ≤5pA bias current across ±10V common-mode range. Its dielectric isolation eliminates substrate leakage paths, while on-chip guarding minimizes parasitic currents in high-Z nodes.
Laser trimming of thin-film resistors achieves ≤2mV offset and 3µV/°C drift; open-loop gain exceeds 110dB with 86dB min CMRR, supporting precision closed-loop configurations in DC-coupled instrumentation circuits.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Noise | 6nV/√Hz typ at 10kHz - enables sub-µV signal resolution in 10kHz bandwidth applications |
| Input Bias Current | ≤5pA max - supports >100GΩ source impedances without significant error |
| Input Offset Voltage | ≤2mV max - reduces initial DC error in precision amplification stages |
| Offset Drift | 3µV/°C typ - maintains accuracy over industrial temperature range (0°C to +70°C) |
| Open-Loop Gain | 110dB min - ensures <0.01% gain error in unity-gain buffer configurations |
| CMRR | 86dB min - rejects common-mode interference in differential sensor readouts |
| Slew Rate | 2V/µs - supports 32kHz full-power response for 20Vp-p signals into 2kΩ load |
Pinout & Package
OPA121KU-TI is housed in an 8-pin SOIC (Package Drawing D), 1.75mm max height, RoHS-compliant with NiPdAu lead finish and JEDEC MSL Level-3 rating.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | Offset Trim (–) | Connects to wiper of 100kΩ potentiometer for manual offset nulling; unused in most applications |
| 2 | Inverting Input (–In) | High-impedance FET input node; requires guarding to prevent leakage-induced errors |
| 3 | Non-Inverting Input (+In) | Dielectrically isolated FET input; bias current unaffected by common-mode voltage shifts |
| 4 | –VCC | Negative supply rail; loss does not destroy device unlike BIFET amplifiers |
| 5 | Offset Trim (+) | Connects to one end of trim potentiometer; referenced to +VCC for symmetric adjustment |
| 6 | Output | Capable of ±11V swing into 2kΩ load; stable with up to 1000pF capacitive loads |
| 7 | +VCC | Positive supply rail; operates from ±5V to ±18V with derated performance |
| 8 | Substrate / Case | Must connect to guard plane or ground to shield input stage from noise and leakage |
Key Features
| Feature | Design Value |
|---|---|
| Difet® dielectric isolation | Eliminates substrate leakage paths, enabling stable ≤5pA bias current independent of common-mode voltage |
| Cascode input architecture | Reduces flicker noise contribution and prevents bias current increase with input voltage swing |
| Laser-trimmed thin-film resistors | Delivers ≤2mV offset and 3µV/°C drift without external calibration components |
| On-chip guarding capability | Pin 8 connection to guard plane minimizes board-level leakage and EMI pickup in high-Z circuits |
| Standard 741 pinout compatibility | Allows drop-in replacement in existing designs without layout changes or footprint rework |
Applications
| Optoelectronics Interface | Data Acquisition Front-End |
|---|---|
Use Scenario: Amplifying low-level photocurrent from photodiodes in spectrophotometers and fiber-optic receivers. IC Role / Device Role / Timing Role: Transimpedance amplifier with ultra-low input bias current to preserve signal integrity. Use Value: ≤5pA bias current prevents dark-current error in picoamp-level photocurrent measurement. | Use Scenario: Conditioning analog outputs from precision ADCs and multiplexed sensor arrays in automated test equipment. IC Role / Device Role / Timing Role: Buffer and gain-stage amplifier with low noise and stable DC accuracy. Use Value: 6nV/√Hz noise and 3µV/°C drift maintain 16-bit+ effective resolution over temperature. |
| Medical Instrumentation | Radiation-Hardened Signal Chain |
Use Scenario: Biopotential amplification in EEG/ECG systems where electrode-skin interface impedance exceeds 10MΩ. IC Role / Device Role / Timing Role: First-stage instrumentation amplifier input with guarded high-Z inputs. Use Value: Pin 8 substrate connection enables full guarding of input traces, suppressing 50/60Hz hum pickup. | Use Scenario: Signal conditioning in nuclear monitoring equipment exposed to ionizing radiation. IC Role / Device Role / Timing Role: Radiation-tolerant front-end amplifier due to dielectric isolation eliminating latch-up paths. Use Value: Difet® construction provides inherent resistance to total ionizing dose (TID) effects vs. standard bipolar or MOSFET op-amps. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar precision FET op-amp applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| OPA128SM | Lower 1/f noise (0.1µVp-p), higher 0.1Hz–10Hz noise floor; 2.5mA quiescent current vs. 4.5mA | Better suited for sub-Hz biomedical measurements; less optimal for battery-powered systems | Select OPA128SM only when ultra-low 0.1Hz–10Hz noise dominates system requirements |
| AD549K | Higher 60pA max bias current; no cascode input → bias current rises with common-mode voltage | Less stable in varying common-mode environments; requires tighter input voltage control | Choose AD549K only if legacy design compatibility outweighs OPA121KU-TI's bias current stability advantage |
Compared with OPA121KU-TI, OPA128SM offers lower 1/f noise but higher power consumption, while AD549K lacks cascode stabilization-making OPA121KU-TI the optimal balance of ultra-low bias current stability, low broadband noise, and SOIC manufacturability.
Availability
OPA121KU-TI is available at Aetrix Electronics and suitable for optoelectronics interfaces, medical instrumentation, data acquisition front-ends, and radiation-hardened signal chains requiring stable component supply across extended production cycles.
Supply support for OPA121KU-TI 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 is a global semiconductor company headquartered in Dallas, Texas, specializing in analog and embedded processing technologies with broad industrial, automotive, and communications product portfolios.
The OPA121KU-TI belongs to TI's precision operational amplifier product line, designed specifically for high-impedance, low-noise, low-drift signal conditioning in instrumentation, medical, and test equipment applications.
FAQ
What is the maximum operating temperature range for the OPA121KU-TI?
The OPA121KU-TI is specified for operation from 0°C to +70°C ambient temperature. Its storage temperature range extends from –55°C to +125°C, and it can withstand soldering temperatures up to +260°C for 3 seconds. The device remains functional outside the specification range down to –25°C, though electrical parameters may degrade beyond the guaranteed limits.
Does the OPA121KU-TI require external offset trimming in typical applications?
No, the OPA121KU-TI uses laser-trimmed thin-film resistors to achieve ≤2mV input offset voltage and 3µV/°C drift, eliminating the need for external trimming in most applications. External nulling via pins 1 and 5 is optional and recommended only when sub-millivolt DC accuracy is required; note that each 100µV of adjusted offset adds ~0.3µV/°C to drift.
How does the OPA121KU-TI handle input overvoltage conditions?
The OPA121KU-TI requires input current limiting resistors only when input voltage falls more than 6V below –VCC. A 10kΩ series resistor safely limits input current to <1µA even with ±15V input levels and lost supply rails. Unlike conventional BIFET amplifiers, it cannot be destroyed by loss of –VCC alone due to its dielectric isolation architecture.
Can the OPA121KU-TI drive capacitive loads without instability?
Yes, the OPA121KU-TI is stable with up to 1000pF capacitive loads in unity-gain configuration. Its internal compensation and cascode architecture provide phase margin of ~65°, allowing direct driving of ADC input capacitors, coaxial cables, or long PCB traces without external isolation resistors-provided pin 8 (substrate) is properly connected to guard or ground.
Is the OPA121KU-TI pin-compatible with standard 741-based layouts?
Yes, the OPA121KU-TI uses the standard 8-pin SOIC footprint matching the 741 op-amp pinout: pin 2 (–In), pin 3 (+In), pin 4 (–VCC), pin 6 (Output), pin 7 (+VCC), and pin 8 (Substrate). This allows direct replacement in existing 741-based designs without PCB modifications, though pin 8 must be connected to guard or ground rather than left floating.
OPA121KU-TI Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- Difet®
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Amplifier Type:
- General Purpose
- Number of Circuits:
- 1
- Output Type:
- -
- Slew Rate:
- 2V/µs
- Gain Bandwidth Product:
- 2 MHz
- -3db Bandwidth:
- -
- Current - Input Bias:
- 1 pA
- Voltage - Input Offset:
- 500 µV
- Current - Supply:
- 2.5mA
- Current - Output / Channel:
- 10 mA
- Voltage - Supply Span (Min):
- 10 V
- Voltage - Supply Span (Max):
- 36 V
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
OPA121KU-TI FAQ
1.How can I place an order for OPA121KU-TI through Aetrix?
Please submit a Request for Quotation (RFQ) for OPA121KU-TI 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 OPA121KU-TI reliable?
The price and inventory of OPA121KU-TI are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for OPA121KU-TI is usually 5 days.
3.What payment methods are accepted for OPA121KU-TI?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for OPA121KU-TI transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for OPA121KU-TI?
OPA121KU-TI orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your OPA121KU-TI 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 OPA121KU-TI?
For technical support, including OPA121KU-TI datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your OPA121KU-TI requirements.
6.How does Aetrix verify that OPA121KU-TI is sourced from the original manufacturer or authorized distributors?
All OPA121KU-TI 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 OPA121KU-TI meets industry standards.
7.What is the process for return or replacement of OPA121KU-TI?
All OPA121KU-TI units undergo pre-shipment inspection (PSI). If there is an issue with OPA121KU-TI, 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 OPA121KU-TI part is unused and in its original packaging.
Return procedure for OPA121KU-TI:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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