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Texas Instruments OPA687U
- Part No.:
- OPA687U
- Manufacturer:
- Texas Instruments
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
OPA687U.pdf
- Description:
- IC OPAMP VFB 3.8GHZ SGL 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:5,093
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Product details
Overview
OPA687U from Texas Instruments is a wideband, ultra-low-noise voltage-feedback operational amplifier with power-down functionality. It delivers 3.8GHz gain bandwidth, 0.95nV/√Hz input voltage noise, and 900V/µs slew rate while operating at ±5V supply and dissipating only 18mA quiescent current. It is used as a high-dynamic-range ADC driver in ultrasound and fiber-optic receiver systems.
For engineers reviewing the OPA687U datasheet, OPA687U pinout, OPA687U application, or OPA687U equivalent, key selection criteria include its guaranteed stability at G ≥ +12, low distortion (–95dBc at 5MHz), power-down capability (2mW disabled power), and SO-8 package compatibility with high-speed layout requirements.
Technical Context
The OPA687U employs a decompensated voltage-feedback architecture optimized for flat frequency response at G = +20 and stable operation down to G = +12. Its internal compensation enables external techniques for inverting gains, supporting controlled second-order low-pass responses with improved SFDR.
It features a dedicated power-down pin (Pin 8) that reduces quiescent current to ≤400µA when asserted low, with 60ns power-up time and 200ns power-down time. Input stage combines ultra-low voltage noise (0.95nV/√Hz) and low current noise (2.5pA/√Hz), making it suitable for transimpedance and differential ADC driver topologies.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Gain Bandwidth Product | 3.8GHz - enables >100MHz closed-loop bandwidth at G=+12 for high-speed signal conditioning |
| Input Voltage Noise Density | 0.95nV/√Hz @ f >1MHz - critical for preserving SNR in low-level wideband amplification |
| Slew Rate | 900V/µs - supports full-scale transient fidelity for >40MSPS ADCs without slewing distortion |
| Harmonic Distortion | –95dBc (2nd harmonic, 5MHz, RL=500Ω) - ensures clean spectral purity in IF and baseband stages |
| Power-Down Quiescent Current | ≤400µA - reduces system standby power by >99% versus active mode (18mA) |
| Stable Gain Minimum | G ≥ +12 - defines minimum non-inverting gain for unconditional stability without external compensation |
| Supply Voltage Range | ±5V (specified), ±6V (max) - compatible with standard dual-rail analog signal chains |
Pinout & Package
OPA687U is housed in an 8-pin SOIC (SO-8) surface-mount package with θJA = 125°C/W, rated for –40°C to +85°C operation. Pin 1 is NC (no connection); Pin 8 is DIS (power-down control).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | No Connection | Unbonded; must be left floating or grounded per layout best practices |
| 2 | Inverting Input (–) | Differential input node; requires matched trace impedance in high-frequency layouts |
| 3 | Noninverting Input (+) | Differential input node; sensitive to parasitic capacitance due to ultra-low noise design |
| 4 | –VS | Negative supply rail; requires local 6.8µF + 0.1µF decoupling per datasheet Figure 1 |
| 5 | DIS | Active-low power-down control; logic low ≤1.5V disables amplifier; float = enabled |
| 6 | +VS | Positive supply rail; requires local 6.8µF + 0.1µF decoupling per datasheet Figure 1 |
| 7 | Output | Capable of ±3.5V swing into 100Ω; drives 50Ω loads directly with minimal peaking |
| 8 | NC | No connection; not internally bonded; avoid routing signals or planes beneath |
Key Features
| Feature | Design Value |
|---|---|
| Ultra-low input voltage noise | 0.95nV/√Hz enables sub-picoamp equivalent input noise in transimpedance configurations with <1pF diode capacitance |
| High slew rate with low distortion | 900V/µs slew rate maintained with –95dBc 2nd-harmonic distortion at 5MHz supports >12-bit ADC linearity |
| External compensation support | Enables stable inverting operation at arbitrary gains using CS/CF networks-e.g., G=–40 with 500MHz bandwidth |
| Fast power-down control | 60ns power-up / 200ns power-down times allow dynamic power gating in burst-mode receivers |
| Guaranteed stability at G ≥ +12 | Eliminates need for external compensation in fixed-gain +20 ADC driver designs across temperature |
Applications
| Low Distortion ADC Driver | OC-3 Fiber Optic Receiver |
|---|---|
Use Scenario: Driving ADS852 14-bit, 65MSPS ADC in medical imaging front-end with differential input. IC Role / Device Role / Timing Role: Differential voltage gain stage providing 20V/V gain, common-mode level shifting, and noise-limited signal integrity. Use Value: Achieves >85dBc two-tone SFDR up to 25MHz center frequency, enabling full ENOB utilization of 14-bit converter. | Use Scenario: Transimpedance amplifier for 155Mbps OC-3 photodiode receiver with 1pF junction capacitance. IC Role / Device Role / Timing Role: Wideband current-to-voltage converter with 12kΩ transimpedance gain and 100MHz flat bandwidth. Use Value: Delivers 3.0pA/√Hz equivalent input noise-1.2× lower than FET-input alternatives under same CD and bandwidth constraints. |
| Ultrasound Channel Amplifier | Equalizing Receiver |
Use Scenario: Time-gain-control (TGC) amplifier in portable ultrasound beamformer with variable gain and 20MHz bandwidth. IC Role / Device Role / Timing Role: High-slew, low-noise gain block compensating for acoustic attenuation over depth. Use Value: Maintains ≤1.6mV input offset drift over –40°C to +85°C, ensuring baseline stability during thermal cycling. | Use Scenario: Post-amplifier in CATV return-path receiver equalizing cable loss up to 85MHz. IC Role / Device Role / Timing Role: Fixed-gain +20 voltage amplifier with 35MHz 0.1dB gain flatness and 70dB off-isolation. Use Value: Provides 70dB input-to-output isolation when disabled, preventing upstream signal leakage during channel mute. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar voltage-feedback op amp applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| OPA643 | Lower GBP (800MHz), higher input voltage noise (2.3nV/√Hz), no power-down pin | Lacks power-down; unsuitable for burst-mode or battery-powered receivers requiring standby current <1mA | Select OPA643 only if bandwidth <400MHz suffices and ultra-low noise is not required |
| OPA686 | Dual-channel version; identical GBP (1.6GHz per channel), same 1.3nV/√Hz noise, no power-down | Not pin-compatible; requires PCB redesign; lacks DIS function for power sequencing | Choose OPA686 only for space-constrained dual-channel systems where power-down is unnecessary |
Compared with OPA643 and OPA686, the OPA687U uniquely combines 3.8GHz GBP, 0.95nV/√Hz noise, and integrated power-down-enabling high-fidelity, low-power wideband amplification unattainable with either alternative.
Availability
OPA687U is available at Aetrix Electronics and suitable for ultrasound imaging front-ends, OC-3 fiber-optic receivers, and high-speed differential ADC driver applications requiring stable component supply across industrial temperature ranges.
Supply support for OPA687U 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 specializing in analog and embedded processing technologies, with leadership in high-performance op amps and precision signal chain solutions.
The OPA687U belongs to TI's OPA68x family of ultra-wideband, low-noise op amps designed specifically for high-dynamic-range data acquisition, communications infrastructure, and medical imaging signal paths.
FAQ
What is the minimum stable gain for OPA687U and how does it affect PCB layout?
The OPA687U is guaranteed stable for non-inverting gains ≥ +12. Below this, external compensation is required. Layout must minimize parasitic capacitance at the inverting input-especially critical when using G = +12, as peaking up to 14dB may occur. Keep feedback traces short and avoid vias near Pin 2; use ground guard rings around input nodes to preserve 0.95nV/√Hz noise performance in the OPA687U.
Does OPA687U support inverting configuration and what are the layout constraints?
Yes, the OPA687U supports stable inverting operation-for example, G = –40 with 500MHz bandwidth using RG = 50Ω and RF = 2kΩ (Figure 2). Critical constraints include driving the inverting input from a low-impedance source (<5Ω output impedance up to 500MHz) and matching source/load impedances to 50Ω. Any series inductance or trace length >5mm at Pin 2 degrades distortion and bandwidth in the OPA687U.
How does the power-down feature of OPA687U behave electrically and what are its timing specs?
When Pin 8 (DIS) is pulled ≤1.5V, the OPA687U disables its input and output stages, reducing quiescent current to ≤400µA. Power-up time is 60ns (typ), power-down time is 200ns (typ), and off-isolation exceeds 70dB at 5MHz. The DIS pin draws ≤160µA bias current; floating DIS enables normal operation. This behavior is fully characterized from –40°C to +85°C for the OPA687U.
Can OPA687U be used in transimpedance applications and what feedback capacitor value is needed for 12kΩ gain?
Yes-the OPA687U is optimized for wideband transimpedance amplifiers. For 12kΩ gain with 1pF photodiode capacitance plus 3.7pF total input capacitance (1.2pF CM + 2.5pF diff), the recommended CF is 0.16pF to achieve ~100MHz Butterworth bandwidth. This value is derived from √(GBP/(4πRFCD)) and validated in Figure 3 of the OPA687U datasheet SBOS065A.
What decoupling is required for OPA687U to maintain 3.8GHz bandwidth and low distortion?
The OPA687U requires parallel decoupling on both +VS (Pin 6) and –VS (Pin 4): a 6.8µF tantalum (or low-ESR ceramic) plus a 0.1µF X7R ceramic placed within 2mm of each supply pin. Ground vias must be placed adjacent to each capacitor pad. Failure to meet this requirement causes >3dB peaking above 100MHz and increases 2nd-harmonic distortion by >10dB in the OPA687U.
OPA687U Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- SpeedPlus™
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Amplifier Type:
- Voltage Feedback
- Number of Circuits:
- 1
- Output Type:
- -
- Slew Rate:
- 900V/µs
- Gain Bandwidth Product:
- 3.8 GHz
- -3db Bandwidth:
- -
- Current - Input Bias:
- 20 µA
- Voltage - Input Offset:
- 100 µV
- Current - Supply:
- 18.5mA
- Current - Output / Channel:
- 80 mA
- Voltage - Supply Span (Min):
- 10 V
- Voltage - Supply Span (Max):
- 32 V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
OPA687U FAQ
1.How can I place an order for OPA687U through Aetrix?
Please submit a Request for Quotation (RFQ) for OPA687U 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 OPA687U reliable?
The price and inventory of OPA687U are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for OPA687U is usually 5 days.
3.What payment methods are accepted for OPA687U?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for OPA687U transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for OPA687U?
OPA687U orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your OPA687U 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 OPA687U?
For technical support, including OPA687U datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your OPA687U requirements.
6.How does Aetrix verify that OPA687U is sourced from the original manufacturer or authorized distributors?
All OPA687U 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 OPA687U meets industry standards.
7.What is the process for return or replacement of OPA687U?
All OPA687U units undergo pre-shipment inspection (PSI). If there is an issue with OPA687U, 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 OPA687U part is unused and in its original packaging.
Return procedure for OPA687U:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
OPA687U Tags
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LM358DT
STMicroelectronics
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LM358DR
Texas Instruments
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LM358ADR
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MCP6006T-E/OT
Microchip Technology
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MCP6006UT-E/OT
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LM324PWR
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LM2902DR
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LM358P
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