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Texas Instruments OPA643NB/250
- Part No.:
- OPA643NB/250
- Manufacturer:
- Texas Instruments
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- SC-74A, SOT-753
- Datasheet:
-
OPA643NB/250.pdf
- Description:
- IC OPAMP VFB 800MHZ SGL SOT23-5
- Quantity:
- Payment:
- Shipping:
Inventory:19,250
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Product details
Overview
OPA643NB/250 from Texas Instruments (formerly Burr-Brown) is a decompensated voltage-feedback operational amplifier optimized for wideband, low-distortion signal conditioning in high-dynamic-range systems. It delivers 800MHz gain-bandwidth product, –90dBc 2nd-harmonic distortion at 5MHz, 2.3nV/√Hz input voltage noise, and ±60mA output drive - enabling use as ADC preamplifier, IF amplifier, or transimpedance stage in 20MSPS digitizers.
For engineers reviewing the OPA643NB/250 datasheet, OPA643NB/250 pinout, OPA643NB/250 application, or OPA643NB/250 equivalent, key selection criteria include stability at gain ≥3, SOT23-5 thermal resistance (150°C/W), 1000V/µs slew rate, and verified SFDR >90dBc at 5MHz with 2Vp-p output swing into 500Ω.
Technical Context
The OPA643NB/250 employs a two-stage decompensated voltage-feedback architecture that enables high open-loop gain (95dB) and wide bandwidth while maintaining classic differential input benefits - including low inverting current noise and bias current cancellation. Its internal compensation targets optimal flatness at noise gain +5, extending closed-loop bandwidth to >200MHz despite an 800MHz GBP.
Stability requires minimum noise gain of 3; external compensation (e.g., RI across inputs or CS/CF networks) enables controlled low-gain operation down to noise gain 2 without sustained oscillation. The SOT23-5 package's short bond wires reduce parasitic inductance, yielding lower 2nd-harmonic distortion than SO-8 or DIP variants under identical 5MHz test conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Gain-Bandwidth Product | 800MHz - sets theoretical bandwidth limit; actual closed-loop bandwidth exceeds 200MHz at G = +5 due to phase-margin optimization |
| Slew Rate | 1000V/µs - supports full-scale 2Vp-p step response in ≤7.5ns (1% settling), critical for fast ADC driving |
| Input Voltage Noise | 2.3nV/√Hz - enables low-noise preamplification of weak signals (e.g., photodiode currents) without dominating system noise floor |
| Harmonic Distortion | –90dBc at 5MHz - measured 2nd-harmonic level relative to fundamental; ensures >80dB SFDR in 20MSPS ADS805 interface |
| Output Current Drive | ±60mA - sustains 2Vp-p into 50Ω load with <0.015° differential phase error at 3.58MHz, suitable for video buffering |
| Supply Voltage Range | ±4.5V to ±5.5V - operates from standard ±5V rails; quiescent current 20–25mA enables 200mW power budget in IF amplifiers |
| Package Thermal Resistance | 150°C/W (θJA) - SOT23-5 variant dissipates heat less efficiently than SO-8 (125°C/W) or DIP (100°C/W), requiring layout-aware derating |
Pinout & Package
SOT23-5 surface-mount package with 1.6mm × 2.9mm footprint, 0.95mm height, and gull-wing leads. Pin 1 marked by beveled corner; device orientation follows JEDEC MO-178.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - Inverting Input (–) | Inverting amplifier input node | Virtual ground in closed-loop configurations; sensitive to parasitic capacitance - keep trace short & guard to minimize pole formation |
| 2 - Non-Inverting Input (+) | Non-inverting amplifier input node | High-impedance differential input; common-mode range extends to ±3.0V - allows rail-to-rail input with ±5V supplies |
| 3 - Output | Amplified signal output | Capable of ±2.75V into 100Ω; series resistor (e.g., 50Ω) required before capacitive loads (e.g., ADC input) to prevent peaking |
| 4 - –VS | Negative supply connection | Must be decoupled with 0.1µF ceramic capacitor near pin; SOT23-5 uses single –VS pin (no dedicated –VS2) |
| 5 - +VS | Positive supply connection | Must be decoupled with 0.1µF ceramic capacitor near pin; no internal split-supply pins - unlike SO-8/DIP variants |
Key Features
| Feature | Design Value |
|---|---|
| Low distortion at high frequency | –90dBc 2nd-harmonic at 5MHz enables >90dB SFDR in 20MSPS digitizer front-ends without post-processing correction |
| High slew rate with low noise | 1000V/µs slew + 2.3nV/√Hz noise permits simultaneous fast transient response and high SNR in IF amplifier stages |
| Gain ≥3 stability without external components | Eliminates need for compensation networks in G = +5 ADC buffer or G = +10 IF amplifier, reducing BOM count and layout complexity |
| SOT23-5 optimized for minimal distortion | Shorter internal bond wires vs. SO-8 reduce inductive coupling, lowering 2nd-harmonic distortion by ~4dB at 5MHz |
| High output current into reactive loads | ±60mA drive supports direct interfacing to 50Ω transmission lines and capacitive ADC inputs when combined with series isolation resistors |
Applications
| ADC Preamplifier | Transimpedance Amplifier |
|---|---|
Use Scenario: AC-coupled front-end for 12-bit, 20MSPS ADS805 ADC in RF digitizer with 10MHz Nyquist zone. IC Role / Device Role / Timing Role: High-speed, low-distortion voltage buffer that maintains >80dB SFDR while centering 2Vp-p signal swing between ±5V rails. Use Value: OPA643NB/250's –90dBc distortion at 5MHz ensures amplifier contribution to SFDR degradation is unmeasurable versus ADS805's native 80dB performance. |
Use Scenario: Wideband photodiode current-to-voltage conversion for optical sensing up to 23MHz bandwidth. IC Role / Device Role / Timing Role: Transimpedance amplifier with 10kΩ gain and 0.8pF feedback capacitor, leveraging 800MHz GBP and 2.3nV/√Hz noise. Use Value: Achieves maximally flat Butterworth response with 23MHz –3dB bandwidth and <0.01% THD, enabled by precise CF calculation using OPA643NB/250's known GBP and input capacitance. |
| IF Amplifier | Video Amplifier |
Use Scenario: Fixed-gain 21.4MHz intermediate-frequency stage in broadband communications receiver. IC Role / Device Role / Timing Role: Non-inverting amplifier with G = +20, delivering >25dBm third-order intercept and <0.005% differential gain error. Use Value: OPA643NB/250's >50dBm intercept below 10MHz and low even-order harmonics outperform fixed-gain IF amps at same 200mW power dissipation. |
Use Scenario: RGB line driver in broadcast-quality video equipment requiring 0.015° differential phase accuracy at 3.58MHz. IC Role / Device Role / Timing Role: Unity-gain buffer with DC-coupled output, driving 150Ω coaxial cable loads. Use Value: OPA643NB/250 achieves 0.015° differential phase error and 0.005% differential gain error - meeting SMPTE 259M specification for HD video distribution. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-speed operational amplifier applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| OPA642U | Unity-gain stable; 500MHz GBP; 1.6nV/√Hz noise; –100dBc distortion at 5MHz | Replaces OPA643NB/250 only where G = +1 is required; sacrifices 300MHz bandwidth and 1000V/µs slew rate | Select OPA642U if unity-gain stability is mandatory and 500MHz bandwidth suffices; not drop-in for G ≥ 3 designs |
| LMH6629MA | Unity-gain stable; 720MHz GBP; 0.94nV/√Hz noise; –92dBc distortion at 5MHz; SO-8 only | Lower noise enables better SNR in preamp stages; lacks SOT23-5 option and requires different layout for thermal management | Choose LMH6629MA for ultra-low-noise preamplification where unity-gain operation is acceptable and SO-8 packaging is viable |
Compared with OPA643NB/250, OPA642U trades bandwidth and slew rate for unconditional stability, while LMH6629MA offers lower noise but no SOT23-5 variant - making OPA643NB/250 uniquely suited for space-constrained, gain ≥3, high-SFDR applications.
Availability
OPA643NB/250 is available at Aetrix Electronics and suitable for high-speed data acquisition, RF instrumentation, optical sensing, and broadcast video systems requiring stable component supply with guaranteed long-term sourcing.
Supply support for OPA643NB/250 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, emphasizing high-performance op amps for test equipment, communications, and industrial measurement.
The OPA643NB/250 belongs to TI's OPA6xx family of decompensated wideband op amps, designed specifically for high-dynamic-range signal chains where distortion, noise, and speed must coexist - such as ADC drivers and IF amplifiers.
FAQ
What is the minimum stable gain for OPA643NB/250?
The OPA643NB/250 requires a minimum noise gain of +3 for unconditional stability. This means non-inverting configurations must use G ≥ +3, and inverting configurations must ensure noise gain (1 + RF/RG) ≥ +3. Operating below this risks sustained oscillation, especially with capacitive loads. External compensation techniques (e.g., RI across inputs) can enable stable G = +2 operation but reduce loop gain and increase integrated noise.
Does OPA643NB/250 support single-supply operation?
No - the OPA643NB/250 is specified only for dual-supply operation from ±4.5V to ±5.5V. Its input common-mode range extends to ±3.0V and output swing reaches ±2.75V into 100Ω, but it lacks rail-to-rail input/output capability and has no internal level-shifting circuitry. For single-supply applications, consider TI's OPA695 or OPA847, which are explicitly characterized for 5V or 12V single-rail use.
How does the SOT23-5 package affect thermal performance of OPA643NB/250?
The OPA643NB/250 in SOT23-5 has a junction-to-ambient thermal resistance (θJA) of 150°C/W - higher than the SO-8 (125°C/W) or DIP (100°C/W) variants. At 25mA quiescent current and ±5V supplies, power dissipation is ~250mW, causing ~37.5°C junction rise above ambient. Layout must include ≥2 cm² copper pour on top/bottom layers with multiple vias to inner ground planes to maintain TJ < 125°C under continuous full-load conditions.
Can OPA643NB/250 drive a 50Ω coaxial cable directly?
Yes - the OPA643NB/250 delivers ±60mA output current and supports ±2.75V into 100Ω, enabling direct 50Ω source termination. Use a series 50Ω resistor at the output (e.g., 0805 chip) placed within 2mm of the OPA643NB/250 pin to match characteristic impedance and suppress reflections. Avoid routing the 50Ω trace over splits in ground plane; maintain continuous return path beneath signal trace for integrity up to 200MHz.
What is the recommended feedback resistor value for OPA643NB/250 in G = +5 configuration?
For G = +5 non-inverting operation, TI recommends RF = 402Ω and RG = 100Ω (or 144Ω for matched 50Ω source/load). Values between 200Ω and 1kΩ optimize distortion vs. noise trade-off: below 200Ω increases output loading and degrades harmonic performance; above 1kΩ introduces ~0.2pF parasitic capacitance that rolls off bandwidth. Always verify layout parasitics with TDR or network analyzer when targeting >100MHz flatness.
OPA643NB/250 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- SC-74A, SOT-753
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Amplifier Type:
- Voltage Feedback
- Number of Circuits:
- 1
- Output Type:
- -
- Slew Rate:
- 1000V/µs
- Gain Bandwidth Product:
- 800 MHz
- -3db Bandwidth:
- -
- Current - Input Bias:
- 19 µA
- Voltage - Input Offset:
- 500 µV
- Current - Supply:
- 20mA
- Current - Output / Channel:
- 65 mA
- Voltage - Supply Span (Min):
- 9 V
- Voltage - Supply Span (Max):
- 11 V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOT-23-5
OPA643NB/250 FAQ
1.How can I place an order for OPA643NB/250 through Aetrix?
Please submit a Request for Quotation (RFQ) for OPA643NB/250 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 OPA643NB/250 reliable?
The price and inventory of OPA643NB/250 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for OPA643NB/250 is usually 5 days.
3.What payment methods are accepted for OPA643NB/250?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for OPA643NB/250 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for OPA643NB/250?
OPA643NB/250 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your OPA643NB/250 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 OPA643NB/250?
For technical support, including OPA643NB/250 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your OPA643NB/250 requirements.
6.How does Aetrix verify that OPA643NB/250 is sourced from the original manufacturer or authorized distributors?
All OPA643NB/250 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 OPA643NB/250 meets industry standards.
7.What is the process for return or replacement of OPA643NB/250?
All OPA643NB/250 units undergo pre-shipment inspection (PSI). If there is an issue with OPA643NB/250, 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 OPA643NB/250 part is unused and in its original packaging.
Return procedure for OPA643NB/250:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
OPA643NB/250 Tags
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