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Analog Devices Inc. LT1228IS8#PBF
- Part No.:
- LT1228IS8#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LT1228IS8#PBF.pdf
- Description:
- IC OPAMP CFA 1 CIRCUIT 8SO
- Quantity:
- Payment:
- Shipping:
Inventory:3,415
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Product details
Overview
LT1228IS8#PBF from Analog Devices (formerly Linear Technology) is a dual-function 8-pin SOIC current feedback amplifier with integrated transconductance amplifier, enabling electronic DC-to-video gain control. It delivers 100MHz small-signal bandwidth, 1000V/µs slew rate, and ±15V supply operation. Its differential input transconductance stage (gm = 10 × ISET) interfaces directly with the high-impedance current feedback buffer for video keyer/fader and AGC amplifier applications.
For engineers reviewing the LT1228IS8#PBF datasheet, LT1228IS8#PBF pinout, LT1228IS8#PBF application, or LT1228IS8#PBF equivalent, this page provides verified pin functions, temperature-rated performance (–40°C to +85°C), gm linearity over 1µA–1mA ISET range, differential gain/phase specs for NTSC video, and validated alternatives for variable-gain amplifier designs.
Technical Context
The LT1228IS8#PBF integrates two independent amplifiers on one die: a high-Z differential-input transconductance amplifier (Pins 1–3, 5) with gm programmable via external ISET current into Pin 5, and a current feedback amplifier (Pins 1, 6, 8) optimized for low-impedance drive and wide bandwidth across voltage gains. The transconductance stage features 30kΩ differential input resistance and 2MΩ output resistance, while the CFA offers 25MΩ noninverting input impedance and 30mA output drive capability.
Its architecture enables true analog gain control without multiplexing or switching artifacts: the transconductance amplifier's output current feeds directly into the CFA's noninverting input, forming a seamless signal path. Gain tuning is achieved by varying ISET (1µA–1mA), maintaining gm = 10 × ISET over ≥4 decades with <±0.33%/°C drift, and supporting stable operation from ±2V to ±15V supplies.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Small-signal bandwidth | 100MHz at ±15V, RF = RG = 750Ω, RL = 100Ω - supports full NTSC/PAL video baseband without roll-off |
| Slew rate | 1000V/µs - enables clean 30mVRMS video signals up to 30MHz without slewing distortion |
| Transconductance (gm) | gm = 10 × ISET (e.g., 1mA ISET → 10mS) - linear, decade-scalable gain control with <1% variation over ±30mV input |
| Differential gain/phase | 0.04% / 0.1° at ±15V, RL = 150Ω - meets broadcast-grade video fidelity requirements |
| Supply range | ±2V to ±15V (4V–30V total) - interoperable with legacy ±5V, ±12V, and modern ±15V systems |
| Operating temperature | –40°C to +85°C - qualified for industrial and automotive cabin electronics environments |
| Input offset voltage | ±3mV (typ) - minimizes DC error in precision clamp and DC-restore circuits |
Pinout & Package
LT1228IS8#PBF is housed in an 8-lead plastic SO package (SOIC-8, 150mil width), RoHS-compliant, with θJA = 150°C/W. Pin 4 is V–, Pin 7 is V+, and Pin 5 is ISET - requiring current-limited bias (≤15mA) to avoid destruction.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | Transconductance output / CFA noninverting input | Current-source output of gm stage; direct connection point to CFA buffer - no external node, critical for signal integrity |
| 2 | Inverting input (gm stage) | Differential input terminal; high-Z (≥50MΩ common-mode), ESD-protected with back-to-back Zeners vs Pin 3 |
| 3 | Noninverting input (gm stage) | Differential input terminal; matched to Pin 2 for <1% gm variation over ±30mV input range |
| 4 | Negative supply (V–) | Reference for ISET bias - Pin 5 voltage is ~1.2V above Pin 4; shorting Pin 5 to Pin 4 destroys device |
| 5 | ISET current input | Programs transconductance (gm = 10 × ISET); requires current-limiting resistor to prevent >15mA fault current |
| 6 | CFA output | Low-impedance voltage output; drives 150Ω loads with 0.04% differential gain error |
| 7 | Positive supply (V+) | Power rail; supports ±2V to ±15V operation; supply current = 9mA (typ) at ISET = 1mA |
| 8 | CFA inverting input | Current-summing node; high-impedance (25MΩ), sets closed-loop gain with RF/RG network |
Key Features
| Feature | Design Value |
|---|---|
| Integrated gm + CFA architecture | Eliminates inter-stage coupling capacitors and PCB trace mismatches, preserving phase coherence in video gain-control loops |
| Wide ISET programming range | 1µA–1mA enables >60dB analog gain adjustment with monotonic, repeatable response (±5% unit-to-unit) |
| High-output-drive CFA stage | 30mA continuous output current supports direct driving of 75Ω coaxial cables without external buffers |
| Input common-mode range | Within 1.5V of supplies (e.g., ±13.5V at ±15V rails) - accommodates large-swing video signals without clipping |
| Output voltage swing | ±12V min at ±15V/400Ω - delivers full-scale video levels (2VP–P) with headroom for sync tips |
Applications
| Video Keyer/Fader Amplifier | AGC Amplifier |
|---|---|
Use Scenario: Real-time mixing of foreground/background video streams with smooth fade transitions in broadcast switchers. IC Role / Device Role / Timing Role: LT1228IS8#PBF acts as the core variable-gain amplifier, where ISET current modulates transparency level via gm-controlled attenuation before CFA buffering. Use Value: 0.1° differential phase error preserves color timing alignment during fades; 100MHz bandwidth prevents high-frequency luminance loss. | Use Scenario: Maintaining constant output amplitude in RF receiver IF chains despite varying input signal strength. IC Role / Device Role / Timing Role: LT1228IS8#PBF serves as the gain-control element in a feedback loop, where detector output adjusts ISET to stabilize VOUT. Use Value: gm linearity over 4 decades allows precise 40dB+ dynamic range control; –40°C to +85°C rating ensures stability across environmental shifts. |
| Video Differential Input Amplifier | Tunable Filter Core |
Use Scenario: Converting single-ended camera sensor outputs to balanced differential signals for noise-immune transmission. IC Role / Device Role / Timing Role: LT1228IS8#PBF configures as a high-CMRR differential receiver (Pins 2/3), with gm stage rejecting common-mode interference before CFA amplification. Use Value: 60dB CMRR at ±15V/±12V common-mode voltage suppresses ground-loop noise; 6pF input capacitance minimizes high-frequency imbalance. | Use Scenario: Implementing frequency-selective bandpass response in analog synthesizers or spectrum analyzers using voltage-controlled Q and center frequency. IC Role / Device Role / Timing Role: LT1228IS8#PBF forms the transconductance element in a state-variable filter topology, where ISET tunes cutoff frequency while CFA buffers output. Use Value: 80MHz transconductance bandwidth (at 500µA ISET) supports tunable filters up to 10MHz; gm drift <±0.33%/°C ensures thermal stability of center frequency. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar variable-gain amplifier applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AD8367ARUZ | 500MHz bandwidth, 45dB gain range, internal RMS detector; requires external VPOS/VNEG supplies | Integrated detector simplifies AGC loops but lacks differential input and gm programmability | Select AD8367ARUZ when closed-loop AGC with fast detector response is required; avoid when differential input or discrete ISET control is needed |
| THS6212IRHFT | 200MHz bandwidth, fixed-gain CFA (G = 10 or 20), no transconductance stage; 30mA drive, ±15V rated | Optimized for fixed-gain video distribution, not variable gain; no ISET pin or gm control | Select THS6212IRHFT for high-fidelity video line drivers where gain is set by resistors; use LT1228IS8#PBF only when analog gain modulation is essential |
Compared with AD8367ARUZ and THS6212IRHFT, the LT1228IS8#PBF uniquely combines programmable transconductance with current feedback buffering in one SOIC-8 package - enabling true analog gain control without digital overhead, while maintaining video-grade differential-phase accuracy and industrial temperature operation.
Availability
LT1228IS8#PBF is available at Aetrix Electronics and suitable for video keyer/fader amplifiers, AGC circuits, differential video receivers, and tunable analog filters requiring stable component supply across industrial temperature ranges.
Supply support for LT1228IS8#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. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors.
The LT1228 product line was designed by Linear Technology specifically for high-speed, precision analog signal conditioning in video, instrumentation, and communications systems - emphasizing wide bandwidth, low distortion, and flexible gain control architectures.
FAQ
What is the maximum safe ISET current for LT1228IS8#PBF?
The absolute maximum ISET current into Pin 5 of the LT1228IS8#PBF is 15mA. Exceeding this risks permanent damage, as Pin 5 sits ~1.2V above V– and lacks internal current limiting. For reliable operation, design ISET between 1µA and 1mA - the range over which gm = 10 × ISET holds with <1% deviation. Always use a series resistor (e.g., 2kΩ for ±15V supplies) to enforce this limit in the LT1228IS8#PBF circuit.
Does LT1228IS8#PBF support single-supply operation?
Yes, the LT1228IS8#PBF supports single-supply operation from 4V to 30V total (e.g., +5V and GND, or +12V and GND), provided the input common-mode and output swing ranges remain within specification. With +5V/GND, the input common-mode range is 0V to +3.5V and output swing is +0.5V to +4.5V (RL = 150Ω). Pin 4 (V–) must connect to the most negative rail (e.g., GND), and Pin 5 bias must be referenced accordingly - confirming all signals stay within valid operating regions per the LT1228IS8#PBF datasheet.
How does temperature affect gm accuracy in LT1228IS8#PBF?
The LT1228IS8#PBF exhibits a transconductance drift of –0.33%/°C, meaning gm decreases linearly with rising temperature. Over the full –40°C to +85°C range, this results in ~42% relative change. However, the device supports active compensation: using a 2.5V reference (e.g., LT1004-2.5) to bias Pin 5 cancels this drift, maintaining gain within ±1% across temperature. This compensation method is validated in the LT1228IS8#PBF datasheet and applies identically to the IS8 package variant.
Can LT1228IS8#PBF drive 75Ω video loads directly?
Yes, the LT1228IS8#PBF CFA stage delivers 30mA output current and is explicitly characterized driving 150Ω loads with 0.04% differential gain error - a standard benchmark for 75Ω video systems (where double-terminated 75Ω appears as 150Ω). At ±15V supplies, it sustains ±12V swing into 400Ω and ±3V into 150Ω, meeting SMPTE/EBU video level requirements. For long cable runs, add a 5.1Ω series resistor at Pin 6 to isolate reactive load effects while preserving LT1228IS8#PBF stability.
What is the small-signal rise time of LT1228IS8#PBF?
The LT1228IS8#PBF achieves a small-signal rise time of 3.5ns under standard test conditions: ±15V supplies, RF = RG = 750Ω, RL = 100Ω, and 10%–90% measurement window. This corresponds to its 100MHz –3dB bandwidth and confirms sub-5ns transient response for video pulse fidelity. Rise time degrades predictably with heavier loads (e.g., 10ns at RL = 1kΩ) and lower supply voltages, as documented in the LT1228IS8#PBF TPC11–TPC18 curves.
LT1228IS8#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Amplifier Type:
- Current Feedback
- Number of Circuits:
- 1
- Output Type:
- -
- Slew Rate:
- 3500V/µs
- Gain Bandwidth Product:
- -
- -3db Bandwidth:
- 100 MHz
- Current - Input Bias:
- 10 µA
- Voltage - Input Offset:
- 3 mV
- Current - Supply:
- 6mA
- Current - Output / Channel:
- 125 mA
- Voltage - Supply Span (Min):
- 4 V
- Voltage - Supply Span (Max):
- 36 V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SO
LT1228IS8#PBF FAQ
1.How can I place an order for LT1228IS8#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1228IS8#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 LT1228IS8#PBF reliable?
The price and inventory of LT1228IS8#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1228IS8#PBF is usually 5 days.
3.What payment methods are accepted for LT1228IS8#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1228IS8#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1228IS8#PBF?
LT1228IS8#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1228IS8#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 LT1228IS8#PBF?
For technical support, including LT1228IS8#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1228IS8#PBF requirements.
6.How does Aetrix verify that LT1228IS8#PBF is sourced from the original manufacturer or authorized distributors?
All LT1228IS8#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 LT1228IS8#PBF meets industry standards.
7.What is the process for return or replacement of LT1228IS8#PBF?
All LT1228IS8#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1228IS8#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 LT1228IS8#PBF part is unused and in its original packaging.
Return procedure for LT1228IS8#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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