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Texas Instruments OPA656U/2K5
- Part No.:
- OPA656U/2K5
- Manufacturer:
- Texas Instruments
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
OPA656U/2K5.pdf
- Description:
- IC VOLTAGE FEEDBACK 1 CIRC 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,441
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Product details
Overview
OPA656U/2K5 from Texas Instruments is a unity-gain stable, FET-input voltage-feedback operational amplifier optimized for ultra-low-noise transimpedance and high-speed data acquisition front-ends. It delivers 550MHz unity-gain bandwidth, 6nV/√Hz input voltage noise, 2pA input bias current, and ±600μV max input offset voltage across –40°C to +85°C - enabling precision optical signal conditioning in photodiode-based OTDR and oscilloscope front-ends.
For engineers reviewing the OPA656U/2K5 datasheet, OPA656U/2K5 pinout, OPA656U/2K5 application, or OPA656U/2K5 equivalent, key selection criteria include its JFET-input low-noise performance at high closed-loop bandwidths, stability under unity-gain conditions, thermal behavior in SOIC-8 packaging, and compatibility with photodiode capacitance compensation up to 23.3pF.
Technical Context
The OPA656U/2K5 uses a high-speed complementary bipolar process with a low-noise JFET input stage, achieving unity-gain stability without external compensation. Its voltage-feedback architecture supports precise gain-setting with standard resistive networks while maintaining 230MHz gain-bandwidth product and 150MHz large-signal bandwidth (2VPP).
It operates from ±4V to ±6V supplies (8V–12V total), features 80dB minimum CMRR and 72dB +PSRR at 25°C, and maintains dc precision via trimmed input offset and drift - critical for transimpedance applications where diode capacitance and feedback pole placement directly impact bandwidth flatness and noise floor.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Unity-gain bandwidth | 550MHz - enables stable buffer operation up to VHF range without peaking or oscillation |
| Gain-bandwidth product | 230MHz - defines maximum achievable closed-loop bandwidth at higher gains (e.g., 23MHz at G=10) |
| Input voltage noise | 6nV/√Hz - dominates integrated noise in transimpedance designs with >10kΩ feedback resistors |
| Input bias current | 2pA (max) - minimizes DC error and leakage-induced drift in high-impedance photodiode interfaces |
| Input offset voltage | ±600μV (max) - ensures <0.1% gain error in 100kΩ transimpedance configurations at room temperature |
| Large-signal bandwidth | 150MHz (2VPP) - supports fast pulse response in active probe and digitizer front-end applications |
| Supply voltage range | 8V to 12V total (±4V to ±6V) - compatible with standard dual-rail lab supplies and isolated DC/DC modules |
Pinout & Package
OPA656U/2K5 is supplied in an 8-pin SOIC (D package), 4.9mm × 6mm body size, with exposed pad not present. Pin functions are validated per TI SBOS196I Rev. F (Feb 2024).
| Pin | Circuit Role | Design Meaning |
|---|---|---|
| 1, 5, 8 | NC | No internal connection - must be left unconnected; no routing or grounding required |
| 2 | VIN– | Inverting input - primary feedback node in transimpedance and inverting amplifier configurations |
| 3 | VIN+ | Noninverting input - referenced to ground or bias voltage; low-current node for high-Z sensor interfaces |
| 4 | –VS | Negative power supply - requires local 0.1μF + 6.8μF decoupling to minimize PSRR degradation above 100kHz |
| 6 | VOUT | Amplifier output - drives 100Ω loads directly; output impedance <10mΩ below 100kHz |
| 7 | +VS | Positive power supply - symmetric rail to –VS; mismatch >0.5V degrades CMRR by ≥10dB |
Key Features
| Feature | Design Value |
|---|---|
| Unity-gain stable architecture | Eliminates need for external compensation components in buffer or G=1 transimpedance layouts |
| JFET input stage | Enables 10¹²Ω common-mode input impedance - preserves signal integrity in high-Z photodiode and probe tip circuits |
| Low distortion at 5MHz | HD2 = –80dBc, HD3 = –100dBc into 200Ω - meets dynamic range requirements for 12-bit+ digitizers |
| Industrial temperature range | Specified from –40°C to +85°C - supports deployment in medical analyzers and field-deployable test equipment |
| ESD robustness | HBM ±2000V - withstands handling and board-level assembly without special ESD controls beyond standard practices |
Applications
| Optical Time-Domain Reflectometry (OTDR) | Oscilloscope Front-End Amplifier |
|---|---|
Use Scenario: Detecting weak backscattered light pulses from fiber-optic cables over distances up to 100km. IC Role / Device Role / Timing Role: Transimpedance amplifier converting photodiode current to voltage with 100kΩ gain and 4MHz bandwidth. Use Value: 6nV/√Hz input voltage noise and 2pA bias current enable sub-picoamp sensitivity while maintaining 550MHz small-signal headroom for pulse fidelity. |
Use Scenario: Signal conditioning of passive probe outputs before ADC sampling in 1GHz-class digital storage oscilloscopes. IC Role / Device Role / Timing Role: Unity-gain buffer isolating probe tip from scope input capacitance while preserving rise time. Use Value: 550MHz unity-gain bandwidth and 1.3ns rise time ensure <1% amplitude error on 500ps edges; SOIC-8 layout supports controlled-impedance PCB routing. |
| Active Probe Tip Amplifier | Medical Laser Pulse Detection |
Use Scenario: Integrating into 10x/100x passive-active hybrid probes for minimal loading of high-frequency circuit nodes. IC Role / Device Role / Timing Role: High-input-impedance, low-noise gain stage placed directly at probe tip to overcome cable loss. Use Value: 10¹²Ω input impedance and 150MHz large-signal bandwidth maintain signal integrity through 1.5m coaxial cable; SOIC-8 thermal resistance (123°C/W) supports localized heatsinking. |
Use Scenario: Converting photocurrent from pulsed laser diode monitoring photodiodes in blood oximetry and flow cytometry systems. IC Role / Device Role / Timing Role: Low-drift transimpedance amplifier capturing nanosecond-scale laser pulses with <100ps jitter. Use Value: ±600μV max VOS and ±6μV/°C drift ensure stable baseline over clinical operating temperatures; 2pA IB prevents diode leakage accumulation during long integration windows. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-speed, low-noise op-amp applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| OPA814 | Higher GBW (250MHz), faster slew rate (750V/μs), lower voltage noise (5.3nV/√Hz), same 1-V/V min gain | Better suited for >200MHz closed-loop bandwidths and lower-noise transimpedance at >1MΩ RF | Select OPA814 when bandwidth >200MHz or noise <5.5nV/√Hz is required; verify layout stability with 5-pin SOT-23 footprint. |
| THS4631 | Wider supply range (±15V), higher slew rate (1000V/μs), but higher voltage noise (7nV/√Hz) and no guaranteed unity-gain stability | Preferred for high-voltage, high-slew applications like pulse amplification, not recommended for precision transimpedance | Choose THS4631 only for ±12V systems requiring >500V/μs slew; avoid in unity-gain or photodiode circuits due to potential instability. |
Compared with OPA656U/2K5, OPA814 offers superior noise and speed for next-generation OTDR front-ends, while THS4631 trades precision and stability for high-voltage swing - making OPA656U/2K5 the optimal balance of unity-gain reliability, JFET input impedance, and 6nV/√Hz noise in industrial optical sensing.
Availability
OPA656U/2K5 is available at Aetrix Electronics and suitable for high-speed data acquisition, optical time-domain reflectometry, and medical laser pulse detection requiring stable component supply across extended temperature ranges and multi-year production cycles.
Supply support for OPA656U/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 is a global semiconductor leader specializing in analog and embedded processing technologies, with over 50 years of op-amp innovation and broad automotive, industrial, and communications portfolio coverage.
The OPA656U/2K5 belongs to TI's high-speed precision op-amp product line, engineered specifically for transimpedance amplification and test-and-measurement front-ends where unity-gain stability, ultra-low noise, and JFET input characteristics are mandatory.
FAQ
What is the maximum supply voltage for OPA656U/2K5?
The OPA656U/2K5 has an absolute maximum total supply voltage of ±6.5V (13V), but its recommended operating range is 8V to 12V (±4V to ±6V). Operation beyond ±6V risks permanent damage per TI SBOS196I Absolute Maximum Ratings. For reliable long-term use in industrial environments, maintain supply within ±5V (10V total) with proper decoupling.
Is OPA656U/2K5 unity-gain stable in all PCB layouts?
Yes, the OPA656U/2K5 is internally compensated for unity-gain stability, but layout-dependent parasitics can still cause peaking or oscillation. TI specifies ≤1dB peaking at G=1 with RF=0Ω and recommends minimizing inverting-node capacitance (<0.5pF) and using direct output-to-inverting-input routing. The SOIC-8 package's 4.9mm × 6mm footprint supports controlled-impedance routing to preserve stability.
Can OPA656U/2K5 drive a 50Ω load directly?
Yes, the OPA656U/2K5 delivers ±3.3V output swing into 100Ω and sustains ±3.1V at full temperature range - sufficient for driving 50Ω loads with appropriate series termination. However, harmonic distortion increases at 5MHz (HD3 = –90dBc into 200Ω); for clean 50Ω transmission, use a 49.9Ω series resistor at the output to isolate reactive load effects and maintain 150MHz large-signal bandwidth.
How does input bias current affect transimpedance accuracy in OPA656U/2K5?
The OPA656U/2K5's 2pA max input bias current introduces <200nV error across a 100kΩ feedback resistor - negligible versus its 600μV offset voltage. In photodiode applications, this allows omission of bias-canceling resistors at VIN+, simplifying layout. At 85°C, IB rises to 5pA max, still contributing <500nV error - well within system-level calibration budgets for medical and test equipment.
What decoupling is required for OPA656U/2K5 in high-frequency operation?
TI mandates local decoupling at both +VS and –VS pins: a 0.1μF ceramic capacitor (X7R, 0805) placed <2mm from each supply pin, plus a 6.8μF tantalum or polymer capacitor within 5mm. This suppresses supply-induced noise above 100kHz and maintains PSRR >70dB. Failure to implement both capacitors degrades 550MHz unity-gain bandwidth by up to 30% and increases output ripple by 12dB.
OPA656U/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:
- Obsolete
- Amplifier Type:
- Voltage Feedback
- Number of Circuits:
- 1
- Output Type:
- -
- Slew Rate:
- 295V/µs
- Gain Bandwidth Product:
- 230 MHz
- -3db Bandwidth:
- 500 MHz
- Current - Input Bias:
- 2 pA
- Voltage - Input Offset:
- 250 µV
- Current - Supply:
- 14mA
- Current - Output / Channel:
- 70 mA
- Voltage - Supply Span (Min):
- 8 V
- Voltage - Supply Span (Max):
- 12 V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
OPA656U/2K5 FAQ
1.How can I place an order for OPA656U/2K5 through Aetrix?
Please submit a Request for Quotation (RFQ) for OPA656U/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 OPA656U/2K5 reliable?
The price and inventory of OPA656U/2K5 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for OPA656U/2K5 is usually 5 days.
3.What payment methods are accepted for OPA656U/2K5?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for OPA656U/2K5 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for OPA656U/2K5?
OPA656U/2K5 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your OPA656U/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 OPA656U/2K5?
For technical support, including OPA656U/2K5 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your OPA656U/2K5 requirements.
6.How does Aetrix verify that OPA656U/2K5 is sourced from the original manufacturer or authorized distributors?
All OPA656U/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 OPA656U/2K5 meets industry standards.
7.What is the process for return or replacement of OPA656U/2K5?
All OPA656U/2K5 units undergo pre-shipment inspection (PSI). If there is an issue with OPA656U/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 OPA656U/2K5 part is unused and in its original packaging.
Return procedure for OPA656U/2K5:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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