Very Fast Low Distortion, Low Noise Differential Amplifiers/ADC Drivers Simplify System Design

Nov 14 2006 - MILPITAS, CA
  • Linear Technology Corporation introduces the LT6402 and LT6411, two new differential amplifiers suitable as high-speed ADC drivers, twisted-pair line drivers and single-ended to differential signal converters. These new products utilize a novel design topology to integrate precision gain-setting resistors on-chip. In addition to simplifying system design and reducing external component count, these devices optimize distortion power and noise performance, critical for high-speed communications applications. With a –3dB bandwidth of 300MHz, the LT6402 is available in three fixed gain options, 6dB, 12dB, and 20dB. Exceptionally low noise and low distortion make the LT6402 ideal for communications transceiver applications as a differential 12- to 14-bit ADC driver, a general-purpose differential gain block, or in other applications requiring differential drive. The LT6402 further minimizes external circuitry and simplifies design by providing an on-chip filter and an output common mode voltage pin (VOCM).

    The LT6411 is a dual-selectable gain amplifier that can be configured to drive differential signals. The gain of each amplifier can be independently selected, resulting in differential gains of –1, +1, and +2 (0dB or 6dB). With a –3dB bandwidth of 650MHz and a slew rate of 3300V/us, the LT6411 achieves very low distortion for input signals up to 70MHz, while consuming only 16mA supply current. During periods of inactivity, the LT6411 can be disabled, dropping current consumption to less than 0.35mA max per amplifier. The LT6411 can be used on split supplies as large as ±6.3V or on a single supply as low as 4.5V.

    "The new LT6411 and LT6402 provide system designers with the flexibility and performance they need to drive high-speed communications and video signals in a wide range of applications," says Brian Black, product marketing manager for Linear Technology's Signal Conditioning product group. "These devices are well suited for driving high-speed ADCs such as Linear Technology's 14-bit 80Msps LTC2249."

    The LT6402 and LT6411 are available now, with prices starting from $2.39 each in quantities of 1,000 pieces.

    Summary of Features: LT6402-6, LT6402-12, LT6402-20

    • Fixed Gain of 6, 12, and 20dB
    • 300 MHz –3dB Bandwidth
    • OIP3 = 48.5dBm, en = 1.9nV/√Hz (LT6402-20, 20MHz)
    • Minimal External Components Required
    • Additional Filtered Outputs
    • Adjustable Output Common Mode Voltage
    • 16-Lead 3mm × 3mm QFN Package

    Summary of Features: LT6411

    • 650MHz –3dB Bandwidth
    • High Slew Rate: 3300V/us
    • User Selectable Gain: +1, +2 and –1
    • No External Resistors Required
    • IM3 = –83dBc at 70MHz
    • Low Supply Current: 16mA total
    • Wide Supply Range: ±2.25V (4.5V) to ±6.3V (12.6V)
    • 3mm × 3mm 16-Pin QFN Package

    Differential Fixed-gain ADC Drivers Simplify System Design


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