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Data Sheet
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User Guides
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Overview

Features and Benefits

  • Very Fast Transconductance Amplifier
    • Bandwidth: 75MHz
    • Outputs Swing Within 0.8V of Supplies
    • gm = 10 × ISET
    • Low THD: 0.2% at 30mVRMS Input
    • Wide ISET Range: 1µA to 1mA
  • Very Fast Current Feedback Amplifier
    • Bandwidth: 100MHz
    • Slew Rate: 1000V/µs
    • Output Drive Current: 30mA
    • Differential Gain: 0.04%
    • Differential Phase: 0.1°
    • High Input Impedance: 25MΩ, 6pF
  • Wide Supply Range: ±2V to ±15V
  • Inputs Common Mode to Within 1.5V of Supplies
  • Supply Current: 7mA
  • Available in 8-Lead PDIP and SOIC Packages

Product Details

The LT1228 makes it easy to electronically control the gain of signals from DC to video frequencies. The LT1228 implements gain control with a transconductance amplifier (voltage to current) whose gain is proportional to an externally controlled current. A resistor is typically used to convert the output current to a voltage, which is then amplified with a current feedback amplifier. The LT1228 combines both amplifiers into an 8-pin package, and operates on any supply voltage from 4V (±2V) to 30V (±15V). A complete differential input, gain controlled amplifier can be implemented with the LT1228 and just a few resistors.

The LT1228 transconductance amplifier has a high impedance differential input and a current source output with wide output voltage compliance. The transconductance, gm, is set by the current that flows into Pin5, ISET. The small signal gm is equal to ten times the value of ISET and this relationship holds over several decades of set current. The voltage at Pin 5 is two diode drops above the negative supply, Pin 4.

The LT1228 current feedback amplifier has very high input impedance and therefore it is an excellent buffer for the output of the transconductance amplifier. The current feedback amplifier maintains its wide bandwidth over a wide range of voltage gains making it easy to interface the transconductance amplifier output to other circuitry. The current feedback amplifier is designed to drive low impedance loads, such as cables, with excellent linearity at high frequencies.

Applications

  • Video DC Restore (Clamp) Circuits
  • Video Differential Input Amplifiers
  • Video Keyer/Fader Amplifiers
  • AGC Amplifiers
  • Tunable Filters
  • Oscillators

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Evaluation Kits (1)

Documentation & Resources

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  • Data Sheets (1)
  • Reliability Data (1)
  • Application Notes (5)
  • User Guides (1)
  • Design Notes (2)
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    Tools & Simulations

    LTspice

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    LT1228

    Design Resources

    ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well.  "Zero defects" for shipped products is always our goal.View our quality and reliability program and certifications for more information.

    Part Number Material Declaration Reliability Data Pin/Package Drawing CAD Symbols, Footprints & 3D Models
    LT1228CN8#PBF Material Declaration Reliability Data 8-Lead PDIP (Narrow 0.3 Inch)
    LT1228CS8#PBF Material Declaration Reliability Data 8-Lead SOIC (Narrow 0.15 Inch)
    LT1228CS8#TRPBF Material Declaration Reliability Data 8-Lead SOIC (Narrow 0.15 Inch)
    LT1228IN8#PBF Material Declaration Reliability Data 8-Lead PDIP (Narrow 0.3 Inch)
    LT1228IS8#PBF Material Declaration Reliability Data 8-Lead SOIC (Narrow 0.15 Inch)
    LT1228IS8#TRPBF Material Declaration Reliability Data 8-Lead SOIC (Narrow 0.15 Inch)
    Wafer Fabrication Data R164 Reliability Data

    PCN-PDN Information

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    Select Model for PCN Information
    • LT1228CN8#PBF Production
    • LT1228CS8#PBF Production
    • LT1228CS8#TRPBF Production
    • LT1228IN8#PBF Production
    • LT1228IS8#PBF Production
    • LT1228IS8#TRPBF Production

    Support & Discussions

    LT1228 Discussions

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