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Analog Devices Inc. LT1251CS#PBF
- Part No.:
- LT1251CS#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Video Amps and Modules
- Package:
- 14-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LT1251CS#PBF.pdf
- Description:
- IC AMP CURRENT FEEDBACK 14SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,973
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Product details
Overview
LT1251CS#PBF from Analog Devices (formerly Linear Technology) is a 40MHz current-feedback video fader and DC gain-controlled amplifier in a 14-lead SOIC package. It provides linear, temperature-stable gain control between two inputs with ±1% typical accuracy, 300V/µs slew rate, and <0.02% differential gain/phase-enabling precise composite or RGB video level adjustment in broadcast-grade equipment.
For engineers reviewing the LT1251CS#PBF datasheet, LT1251CS#PBF pinout, LT1251CS#PBF application, or LT1251CS#PBF equivalent, this device is selected for high-fidelity analog video signal routing where low crosstalk, fast control path response (10MHz), and minimal distortion (<0.01% THD at full gain) are critical to maintaining NTSC/PAL signal integrity.
Technical Context
The LT1251CS#PBF implements a dual-input current-feedback architecture with independent unity-gain buffers driving inverting nodes, enabling simultaneous signal mixing and gain interpolation. Its control path uses an internal transconductance stage converting VC (Pin 3) to a current ratio K that sets input contribution from 0% to 100% without requiring external DACs or precision references.
Unlike the LT1256, the LT1251CS#PBF includes zero/full-scale clamping circuitry: below 2% or above 98% VC, it fully disables one input and enables the other-eliminating off-channel feedthrough caused by offset errors in control signals. This makes it optimal for fader and keyer applications demanding clean channel isolation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Small-signal bandwidth | 40MHz at ±15V supply - supports full NTSC/PAL baseband video without attenuation |
| Slew rate | 300V/µs - ensures distortion-free reproduction of fast video transients (e.g., sync pulses) |
| Gain accuracy | ±1% typical, ±3% max over 0–100% control range - enables calibrated gain setting without trimming |
| Differential gain/phase | 0.02%/0.02° at 0% or 100% control - preserves color fidelity in composite video systems |
| Control path bandwidth | 10MHz - allows real-time fader transitions synchronized with video frame timing |
| Output current | ±40mA - drives 75Ω coaxial lines or multiple downstream amplifiers directly |
| Supply range | ±2.5V to ±15V (or single 5V to 30V) - supports both portable and studio-grade power architectures |
Pinout & Package
LT1251CS#PBF is housed in a 14-lead plastic SOIC (S package) with θJA = 100°C/W, suitable for surface-mount reflow assembly and moderate-power video signal chains.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 14 | Noninverting inputs (IN1, IN2) | High-impedance (17MΩ || 1.5pF) video signal entry points; require local RC damping if driven by long cables |
| 2, 13 | Inverting inputs (FB1, FB2) | Current-feedback nodes; voltage follows noninverting input; sensitive to stray capacitance |
| 3 | Control voltage (VC) | Analog gain interpolation input (0–2.5V); LT1251 clamps at 2%/98% for clean fader endpoints |
| 4, 11 | Full-scale reference inputs (FS, IFS) | Set gain scaling; internal 5kΩ resistors enable operation with only VFS = 2.5V applied |
| 5, 10 | Internal resistor terminals (RC, RFS) | Exposed for external gain calibration or bypass; open-circuit by default |
| 6 | Null adjust (NULL) | DC offset correction node; accepts op-amp output referenced to V– for precision nulling |
| 7, 9 | Power supplies (V–, V+) | Support ±2.5V to ±15V; bypassing with 0.01–0.1µF + 4.7µF per rail required for stability |
| 8, 12 | Ground reference (GND) | Signal ground pins; must connect to low-impedance ground plane to minimize video noise |
Key Features
| Feature | Design Value |
|---|---|
| Zero/full-scale clamping | Automatically disables one input below 2% or above 98% VC-eliminates off-channel feedthrough in fader mode |
| Temperature-compensated gain | ±50ppm/°C drift (N package) or ±400ppm/°C (S package)-maintains consistent video levels across operating range |
| Low control feedthrough | 2.5mVP-P - prevents control voltage ripple from modulating output video signal |
| Fast settling time | 65ns to 0.1% for 2V step - enables frame-accurate gain transitions in digital video switchers |
| Wide supply flexibility | Operates from ±2.5V to ±15V or single 5V to 30V-compatible with legacy and modern video system rails |
Applications
| Composite Video Gain Control | RGB/YUV Video Fading |
|---|---|
Use Scenario: Adjusting luminance/chrominance levels in analog SD/HD broadcast encoders before transmission. IC Role / Device Role / Timing Role: Dual-input fader interpolating between baseband video sources while preserving NTSC/PAL timing and amplitude integrity. Use Value: Achieves <0.02% differential gain error-critical for maintaining color saturation and hue accuracy across gain settings. | Use Scenario: Real-time crossfading between camera feeds in live production switchers. IC Role / Device Role / Timing Role: High-speed analog mixer with 10MHz control path enabling sub-frame fader transitions. Use Value: 300V/µs slew rate prevents transient distortion during rapid gain changes, ensuring glitch-free video output. |
| Video Keyer Circuits | Gamma Correction Amplifiers |
Use Scenario: Generating clean chroma-key masks in analog character generators and overlay systems. IC Role / Device Role / Timing Role: Precision-controlled amplifier acting as alpha channel generator with hard on/off switching at VC extremes. Use Value: Zero/full-scale clamping ensures complete channel isolation (<–80dB off-channel rejection) when keying is inactive. | Use Scenario: Applying nonlinear brightness correction to CRT monitor drive signals or legacy display interfaces. IC Role / Device Role / Timing Role: Programmable gain stage configured with external resistive ladder to implement gamma curve shaping. Use Value: ±1% gain accuracy enables repeatable, factory-calibrated gamma profiles without software compensation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar video fader and gain control applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1256CS#PBF | Lacks zero/full-scale clamping; operates linearly across full 0–100% VC range with ±3% gain accuracy. | Better suited for applications requiring >20dB linear control range (e.g., programmable filters, modulators). | Select LT1256CS#PBF only when continuous linear interpolation-not endpoint clamping-is required. |
| AD8340ACPZ-R7 | RF digital VGA (400MHz) with SPI interface; 30dB gain range; requires external clock and digital control. | Targets RF/video IF gain control in digital infrastructure; not pin-compatible or functionally equivalent for baseband analog faders. | Choose AD8340ACPZ-R7 only for digitally controlled RF/IF paths-not for analog video fader replacement. |
Compared with LT1256CS#PBF and AD8340ACPZ-R7, the LT1251CS#PBF uniquely delivers analog fader functionality with hardware-enforced endpoint isolation, eliminating need for external logic or calibration to achieve clean channel switching in broadcast video systems.
Availability
LT1251CS#PBF is available at Aetrix Electronics and suitable for broadcast video equipment, professional video switchers, and analog test instrumentation requiring stable component supply, guaranteed commercial-grade temperature performance (0°C to 70°C), and long-term obsolescence management.
Supply support for LT1251CS#PBF 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
Analog Devices, Inc. (ADI) is a global semiconductor leader specializing in high-performance analog, mixed-signal, and digital signal processing technologies for precision measurement and signal conditioning.
The LT1251CS#PBF belongs to ADI's legacy Linear Technology video amplifier product line, engineered specifically for broadcast-quality analog video signal processing-including fader, keyer, and gain control functions in professional video infrastructure.
FAQ
What is the maximum recommended feedback resistor value for LT1251CS#PBF to maintain 40MHz bandwidth?
The LT1251CS#PBF achieves its full 40MHz small-signal bandwidth at ±15V supply with RF = 1.3kΩ and RL = 100Ω. Increasing RF reduces bandwidth-e.g., RF = 1.5kΩ yields ~30MHz at ±5V. For 40MHz operation, keep RF ≤ 1.3kΩ and minimize stray capacitance at Pins 2 and 13 using tight layout and local grounding.
Does LT1251CS#PBF require external resistors for basic fader operation?
No. The LT1251CS#PBF integrates internal 5kΩ control (RC) and full-scale (RFS) resistors. With VFS = 2.5V applied to Pin 11 and VC (0–2.5V) on Pin 3, only external feedback resistors (e.g., RF1 = RF2 = 1.5kΩ) and supply bypass capacitors are needed for functional two-input fader operation.
How does the NULL pin (Pin 6) function in LT1251CS#PBF?
The NULL pin adjusts internal current mirror bias to correct output DC offset. With IFS flowing through 200Ω to V–, Pin 6 sits ~100mV above V–. An op-amp (e.g., LT1077) driving Pin 6 within millivolts of V– can null output offset to <1mV-critical for AC-coupled video systems requiring zero DC shift.
What is the minimum supply voltage required for LT1251CS#PBF to operate with 2.5V control signals?
The LT1251CS#PBF requires ≥4.5V total supply (e.g., ±2.5V or +5V/0V) to support 2.5V VC and VFS signals. At lower supplies, the internal control amplifiers cannot swing sufficiently-causing gain nonlinearity or failure to reach full scale. Always verify V+ ≥ VFS + 0.5V and V– ≤ –0.5V for reliable 2.5V reference operation.
Can LT1251CS#PBF drive a 75Ω video load directly?
Yes. The LT1251CS#PBF delivers ±40mA output current and maintains ±3.0V swing into 150Ω. When driving 75Ω, use RF = 1.5kΩ and add a series 75Ω termination at the output to match impedance and prevent reflections-achieving full NTSC compliance with <0.02% differential gain error.
LT1251CS#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Package/Case:
- 14-SOIC (0.154", 3.90mm Width)
- Series:
- -
- Packaging:
- Tube
- Product Status:
- Active
- Applications:
- Current Feedback
- Output Type:
- -
- Number of Circuits:
- 1
- -3db Bandwidth:
- 40 MHz
- Slew Rate:
- 300V/µs
- Current - Supply:
- 14.5 mA
- Current - Output / Channel:
- 40 mA
- Voltage - Supply, Single/Dual (±):
- 5V ~ 30V, ±2.5V ~ 15V
- Mounting Type:
- Surface Mount
- Grade:
- -
- Qualification:
- -
- Supplier Device Package:
- 14-SO
LT1251CS#PBF FAQ
1.How can I place an order for LT1251CS#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1251CS#PBF 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 LT1251CS#PBF reliable?
The price and inventory of LT1251CS#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1251CS#PBF is usually 5 days.
3.What payment methods are accepted for LT1251CS#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1251CS#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1251CS#PBF?
LT1251CS#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1251CS#PBF 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 LT1251CS#PBF?
For technical support, including LT1251CS#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1251CS#PBF requirements.
6.How does Aetrix verify that LT1251CS#PBF is sourced from the original manufacturer or authorized distributors?
All LT1251CS#PBF 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 LT1251CS#PBF meets industry standards.
7.What is the process for return or replacement of LT1251CS#PBF?
All LT1251CS#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1251CS#PBF, 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 LT1251CS#PBF part is unused and in its original packaging.
Return procedure for LT1251CS#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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