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AD8368:  800 MHz, LINEAR-IN-dB VGA with AGC Detector

Product Details

Product Status:Recommended for New Designs

The AD8368 is a variable gain amplifier (VGA) with analog linear-in-dB gain control that can be used from low frequencies to 800 MHz. Its excellent gain range, conformance, and flatness are attributed to the Analog Devices, Inc. X-AMP® architecture, an innovative technique for implementing high performance variable gain control.

The gain range of −12 dB to +22 dB is scaled accurately to 37.5 dB/V with excellent conformance error. The AD8368 has a 3 dB bandwidth of 800 MHz that is nominally independent of gain setting. At 140 MHz, the OIP3 is 33 dBm at maximum gain. The output noise floor is −143 dBm/Hz, which corresponds to a 9.5 dB noise figure at maximum gain. The single-ended input and output impedances are nominally 50 Ω.

The gain of the AD8368 can be configured to be an increasing or decreasing function of the gain control voltage depending on whether the MODE pin is pulled to the positive supply or to ground, respectively. When MODE is pulled high, the AD8368 operates as a typical VGA with increasing gain.

By connecting MODE to ground and using the on-board rms detector, the AD8368 can be configured as a complete automatic gain control (AGC) system with RSSI. The output power is accurately leveled to the internal default setpoint of 63 mV rms (−11 dBm referenced to 50 Ω), independent of the waveform crest factor. Because the uncommitted detector input is available at DETI, the AGC loop can level the signal at the AD8368 output or at any other point in the signal chain over a maximum input power range of 34 dB. Furthermore, the setpoint level can be raised by dividing down the output signal before applying it to the detector.

The AD8368 operates from a supply voltage of 4.5 V to 5.5 V and consumes 60 mA of current. It can be fully powered down to <3 mA by grounding the ENBL pin. The AD8368 is fabricated using the Analog Devices proprietary SiGe SOI complementary bipolar IC process. It is available in a 24-lead LFCSP and operates over the industrial temperature range of −40°C to +85°C. Application boards are available upon request.


  • Complete IF AGC amplifiers
  • Gain trimming and leveling
  • Cellular base stations
  • Point-to-point radio links
  • RF instrumentation
  • Data Sheet, Rev. B, 09/2008


    • Analog variable gain range: −12 dB to +22 dB
    • Linear-in-dB scaling: 37.5 dB/V
    • 3 dB bandwidth: 800 MHz @ VGAIN = 0.5 V
    • Integrated rms detector
    • P1dB: 16 dBm @ 140 MHz
    • Output IP3: 33 dBm @ 140 MHz
    • Noise figure at maximum gain: 9.5 dB @ 140 MHz
    • Input and output impedances: 50 Ω
    • Single-supply voltage from 4.5 V to 5.5 V
    • RoHS-compliant, 24-lead LFCSP

    Functional Block Diagram for AD8368

    Design Tools,Models,Drivers & Software

    Title Content Type File Type
    ADI’s ADIsimRF design tool provides calculations for the most important parameters within the RF signal chain, including cascaded gain, noise figure, IP3, P1dB, and total power consumption.
    ADIsim Design/Simulation Tools HTML
    ADIsimPLL™- Version 3.60.10
    ADIsimPLL enables the rapid and reliable evaluation of new high performance PLL products from ADI. It is the most comprehensive PLL Synthesizer design and simulation tool available today. Simulations performed include all key non-linear effects that are significant in affecting PLL performance. ADIsimPLL removes at least one iteration from the design process, thereby speeding the design- to-market.
    ADIsim Design/Simulation Tools HTML

    Evaluation Kits & Symbols & Footprints

    Evaluation Boards & KitsView the Evaluation Boards and Kits page for documentation and purchasing

    Symbols and Footprints— Analog Devices offers Symbols & Footprints which are compatible with a large set of today’s CAD systems for broader and easier support.

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    AD8368 Model Options
    Price Table Help

    The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.

    AD8368 Evaluation Board
    Model Description Price RoHS View PCN/ PDN Check Inventory/
    AD8368-EVALZ Status: Production Evaluation Board $100.19 Yes -

    Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.

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