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Analog Devices Inc. LT1228CN8#PBF
- Part No.:
- LT1228CN8#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- 8-DIP (0.300", 7.62mm)
- Datasheet:
-
LT1228CN8#PBF.pdf
- Description:
- IC OPAMP CFA 1 CIRCUIT 8DIP
- Quantity:
- Payment:
- Shipping:
Inventory:3,406
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Product details
Overview
LT1228CN8#PBF from Analog Devices (formerly Linear Technology) is a dual-function 8-pin monolithic current feedback amplifier with integrated transconductance amplifier for electronically controlled DC-to-video gain. It delivers 100MHz small-signal bandwidth, 1000V/µs slew rate, and gm = 10 × ISET over 1µA–1mA ISET range, enabling precise AGC and video keyer/fader circuits in broadcast and instrumentation systems.
For engineers reviewing the LT1228CN8#PBF datasheet, LT1228CN8#PBF pinout, LT1228CN8#PBF application, or LT1228CN8#PBF equivalent, key selection considerations include its dual-amplifier architecture (transconductance + CFA), ±2V to ±15V supply flexibility, differential input common-mode range within 1.5V of rails, output swing within 0.8V of supplies, and 7mA quiescent current at ±15V.
Technical Context
The LT1228CN8#PBF integrates two functionally distinct amplifiers on one die: a high-impedance differential-input transconductance amplifier (Pins 1,2,3,5) whose small-signal transconductance gm scales linearly with externally injected ISET current at Pin 5, and a high-input-impedance current feedback amplifier (Pins 1,6,8) optimized for driving low-Z loads like coaxial cables with minimal phase distortion.
Its architecture enables direct cascading - transconductance amplifier output (Pin 1 current source) feeds the noninverting input of the CFA - eliminating external interstage coupling components. The ISET pin voltage sits ~1.2V above V– (two diode drops), requiring current-limiting protection to avoid destruction if shorted to ground or V+.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Small-signal bandwidth | 100MHz at ±15V, RF = RG = 750Ω, RL = 100Ω - supports NTSC/PAL video signal integrity without gain peaking |
| Slew rate | 1000V/µs - enables clean 30mVRMS input handling at 30MHz with ≤0.2% THD |
| Transconductance (gm) | gm = 10 × ISET (e.g., 1mA ISET → 10mS) - provides linear, decade-spanning gain control via analog current |
| Input common-mode range | Within 1.5V of supplies (±13.5V at ±15V) - accommodates wide dynamic range video inputs without clamping |
| Output voltage swing | ±12V at ±15V/400Ω - delivers full-scale video drive into standard termination loads |
| Supply current | 7mA typical at ±15V, ISET = 0 - enables low-power operation in multi-channel video processing |
| Differential gain/phase | 0.04%/0.1° at ±15V, RL = 150Ω - meets broadcast-grade color fidelity requirements for composite video |
Pinout & Package
LT1228CN8#PBF uses an 8-lead plastic DIP (N8) package with 0.3-inch width and through-hole mounting. Pin 4 is V–, Pin 8 is CFA inverting input, Pin 1 is shared node (transconductance output / CFA noninverting input), Pin 5 is ISET current input, and Pins 2/3 form the differential transconductance input pair.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | Transconductance output / CFA noninverting input | Current-source output of gm amp; directly drives high-Z input of CFA - no external coupling required |
| 2 | Transconductance inverting input | Differential input terminal; high-Z (≥50MΩ common-mode) enables precision DC-coupled gain control |
| 3 | Transconductance noninverting input | Differential input terminal; matched to Pin 2 for <10µV offset and >60dB CMRR |
| 4 | V– (negative supply) | Reference for ISET pin (Pin 5 sits ~1.2V above this); must be current-limited to <15mA into Pin 5 |
| 5 | ISET current input | Externally programmed current sets gm; destruction occurs if shorted to V– or V+ |
| 6 | CFA output | Low-impedance voltage output capable of sourcing/sinking 30mA into 150Ω loads |
| 7 | V+ (positive supply) | Supports ±2V to ±15V operation; PSRR ≥60dB ensures stable gain under supply ripple |
| 8 | CFA inverting input | High-impedance node for resistive feedback; stray capacitance here causes peaking - keep <1pF |
Key Features
| Feature | Design Value |
|---|---|
| Dual-amplifier integration | Eliminates interstage coupling capacitors and bias networks - reduces board area and phase error in video paths |
| Linear gm vs ISET scaling | gm = 10 × ISET holds across 1µA–1mA - enables predictable, temperature-compensatable gain programming |
| Wide supply range | Operates from ±2V to ±15V - supports both low-voltage portable gear and high-swing broadcast equipment |
| Video-optimized linearity | 0.04% differential gain / 0.1° differential phase at 150Ω load - preserves color fidelity in NTSC composite signals |
| High CFA input impedance | 25MΩ || 6pF at ±15V - minimizes loading of transconductance output and preserves bandwidth |
Applications
| Video Differential Input Amplifier | AGC Amplifier |
|---|---|
Use Scenario: Amplifying balanced analog video signals (e.g., SDI receiver outputs or camera sensor interfaces) while rejecting common-mode noise and ground loops. IC Role / Device Role / Timing Role: LT1228CN8#PBF serves as a DC-coupled, gain-controllable differential-to-single-ended converter with rail-to-rail input common-mode range. Use Value: Enables 0.04% differential gain accuracy and 0.1° phase matching across luminance/chrominance channels without external trimming. | Use Scenario: Dynamically adjusting signal amplitude in RF receiver front-ends or optical transceivers to maintain constant output level despite varying input strength. IC Role / Device Role / Timing Role: LT1228CN8#PBF implements analog gain control via ISET current, responding to detector output with sub-10ns settling time. Use Value: Provides 100MHz closed-loop bandwidth and 1000V/µs slew rate to track fast envelope variations without distortion. |
| Video Keyer/Fader Amplifier | Tunable Filter Core |
Use Scenario: Blending multiple video sources (e.g., chroma key compositing in live production switchers) with smooth, flicker-free transitions. IC Role / Device Role / Timing Role: LT1228CN8#PBF acts as a voltage-controlled variable-gain amplifier where ISET current modulates opacity weighting in real time. Use Value: Delivers monotonic, linear gain control over 80dB range (1µA–1mA ISET) with <0.2% THD at 30mVRMS input. | Use Scenario: Constructing active filters (e.g., state-variable or biquad topologies) where center frequency and Q are tuned via analog control voltage. IC Role / Device Role / Timing Role: LT1228CN8#PBF functions as the transconductance element in Gm-C filter designs, with ISET setting cutoff frequency. Use Value: Achieves 80MHz transconductance amplifier bandwidth at 500µA ISET, enabling tunable filters up to 10MHz with low sensitivity to component tolerances. |
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, RMS-detected AGC loop; requires external loop filter and power supply sequencing | Integrated AGC loop simplifies design but adds latency (~1µs); less suitable for sub-microsecond keying | Choose AD8367ARUZ when closed-loop automatic gain control is required and latency is acceptable |
| THS6212IRHFT | 1.8GHz bandwidth, 3000V/µs slew rate, fixed-gain CFA; lacks integrated transconductance stage and ISET control | Requires external VGA or DAC for gain control; better for ultra-high-speed fixed-gain buffering than programmable gain | Choose THS6212IRHFT when maximum bandwidth and drive capability are prioritized over integrated gain control |
Compared with AD8367ARUZ and THS6212IRHFT, the LT1228CN8#PBF uniquely combines transconductance-based analog gain programming with current-feedback output drive in a single 8-pin DIP, offering optimal trade-offs for discrete, low-latency, DC-coupled video gain control without external loop components.
Availability
LT1228CN8#PBF is available at Aetrix Electronics and suitable for video differential input amplifiers, AGC amplifiers, video keyer/fader amplifiers, and tunable filter cores requiring stable component supply and long-term industrial availability.
Supply support for LT1228CN8#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 acquired Linear Technology in 2017 and maintains full product support, datasheet documentation, and application engineering for legacy Linear parts including the LT1228 series.
The LT1228CN8#PBF belongs to Linear's high-speed amplifier product line, designed specifically for precision analog video signal processing, DC-coupled gain control, and wideband instrumentation applications demanding low distortion and fast settling.
FAQ
What is the absolute maximum ISET current for LT1228CN8#PBF?
The LT1228CN8#PBF datasheet specifies an absolute maximum ISET current of 15mA at Pin 5. Exceeding this value - especially if Pin 5 is shorted to ground or V+ - will destroy the device. For reliable operation, ISET should be limited to 1µA–1mA per the typical applications, using a series resistor (e.g., 2kΩ minimum at ±15V) to enforce current limiting. The LT1228CN8#PBF transconductance remains linear and stable within this recommended range.
Can LT1228CN8#PBF operate on single-supply configurations?
Yes, the LT1228CN8#PBF supports single-supply operation from +4V to +30V (e.g., +5V or +12V with ground as V–). Its inputs accept common-mode voltages within 1.5V of either rail, and outputs swing within 0.8V of the rails. When using single supply, Pin 4 (V–) connects to ground, Pin 5 voltage sits ~1.2V above ground, and input/output referencing must be biased accordingly. The LT1228CN8#PBF maintains full 100MHz bandwidth and 0.2% THD performance under these conditions.
What is the purpose of Pin 5 (ISET) in LT1228CN8#PBF?
Pin 5 (ISET) on the LT1228CN8#PBF sets the transconductance (gm) of the internal voltage-to-current amplifier via externally injected current: gm = 10 × ISET. This enables precise, linear, analog-controlled gain adjustment across eight decades (1µA–1mA). The voltage at Pin 5 is ~1.2V above V–, making it incompatible with direct voltage drive - a current source or resistor-to-bias-voltage interface is mandatory. The LT1228CN8#PBF relies entirely on ISET for gain programming; no digital interface or register configuration is involved.
How does LT1228CN8#PBF achieve low differential phase error in video applications?
The LT1228CN8#PBF achieves 0.1° differential phase error at ±15V/150Ω by combining high slew rate (1000V/µs), wide bandwidth (100MHz), and optimized internal compensation that minimizes group delay variation across the 4.43MHz chrominance band. Its current-feedback architecture inherently provides flat phase response up to unity gain, and the matched input transistor pair ensures symmetrical signal path timing. Measured under NTSC composite video conditions, the LT1228CN8#PBF maintains this spec without external peaking networks or phase trim components.
Is LT1228CN8#PBF pin-compatible with other LT1228 variants?
Yes, the LT1228CN8#PBF shares identical pinout and electrical characteristics with all N8-package LT1228 variants (e.g., LT1228IN8#PBF, LT1228CJ8), differing only in temperature grade and packaging material. All use the same 8-lead PDIP footprint, Pin 1–8 assignment, and functional block diagram. The LT1228CN8#PBF is rated for 0°C to 70°C operation and features lead-free (Pb-free) finish, while LT1228IN8#PBF extends to –40°C to 85°C. No PCB layout changes are needed when substituting within the N8 family.
LT1228CN8#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-DIP (0.300", 7.62mm)
- 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:
- -
- Voltage - Supply Span (Min):
- 4 V
- Voltage - Supply Span (Max):
- 36 V
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 8-PDIP
LT1228CN8#PBF FAQ
1.How can I place an order for LT1228CN8#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1228CN8#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 LT1228CN8#PBF reliable?
The price and inventory of LT1228CN8#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1228CN8#PBF is usually 5 days.
3.What payment methods are accepted for LT1228CN8#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1228CN8#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1228CN8#PBF?
LT1228CN8#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1228CN8#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 LT1228CN8#PBF?
For technical support, including LT1228CN8#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1228CN8#PBF requirements.
6.How does Aetrix verify that LT1228CN8#PBF is sourced from the original manufacturer or authorized distributors?
All LT1228CN8#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 LT1228CN8#PBF meets industry standards.
7.What is the process for return or replacement of LT1228CN8#PBF?
All LT1228CN8#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1228CN8#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 LT1228CN8#PBF part is unused and in its original packaging.
Return procedure for LT1228CN8#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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