AD8368:  800 MHz, Linear-in-dB VGA with AGC Detector

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 ...More

AD8368:  800 MHz, Linear-in-dB VGA with AGC Detector

Product Description

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.

Applications

  • Complete IF AGC amplifiers
  • Gain trimming and leveling
  • Cellular base stations
  • Point-to-point radio links
  • RF instrumentation

    • Data Sheet, Rev. B, 09/2008

    Features

    • 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

    Verified Circuits Using This Part

    Verified Circuits are designed for ease of use and proven to work by ADI applications engineers. To learn more about Verified Circuits from ADI, please visit Verified Circuits Home.

    Circuit Diagram

    Diagrams

    AD8368 Diagram
    Functional Block Diagram for AD8368

    技术指标

    Supply Voltage (V) +5V
    Gain Low End (dB) -12dB
    Gain High End (dB) +22dB
    -3 dB BW (MHz) 800MHz
    Gain Accuracy (dB) ±0.4dB
    Package 24-Lead LFCSP

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    Part# Gain Control -3 dB BW (MHz) Gain Low End (dB) Gain High End (dB) Number of Channels Spectral Noise (nV/rtHz) Supply Voltage (V) Supply Current (max) Gain Accuracy (dB) 1 dB Comp Point (dBm) Package Price* (1000-4999)
    AD600 Analog 35 0 +40 2 1.4 ±5 14mA - - - $16.61
    AD602 Analog 35 -10 +30 2 1.4 ±5 14mA - - - $13.36
    AD603 Analog 90 -11 +31 1 1.4 ±5 20mA ±0.5 - 8-Lead DIP, 8-Lead SOIC $4.40
    AD604 Analog 40 0 +48 2 0.8 ±5 31mA ±0.3 15 24-Lead SOIC, 24-Lead SSOP $16.45
    AD605 Analog 40 -14 +34 2 1.8 +5 23mA ±0.2 15 16-Lead SOIC $9.91
    AD8260 Digital 180 -6 +24 1 2.4 +3.3 28mA +0.25 - - $3.84
    AD8320 Digital 150 -10 +26 1 53 +12 105mA ±0.2 22.5 20-Lead SOIC -
    AD8321 Digital 120 -27.4 +26 1 20 +9 90mA ±1 19.5 20-Lead SOIC $4.40
    AD8322 Digital 180 -12.6 +29.5 1 64 +5 113mA ±2 19 28-Lead TSSOP $3.19
    AD8323 Digital 100 -26 +27.5 1 - +5 - - - 28-Lead TSSOP $3.34
    AD8324 Digital 100 -25.5 +33.5 1 157 +3.3 207mA ±1 21 20-Lead LFCSP, 20-Lead QSOP $1.73
    AD8325 Digital 100 -29.5 +30 1 56 +5 133mA ±1 18.5 28-Lead TSSOP $3.34
    AD8326 Digital 100 -26 +27.5 1 100 ±5