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High Speed Amp for driving ADS5562

Robert Murano
Intellectual 1225 points
Other Parts Discussed in Thread: ADS5562, THS4513, THS4509

I am interested in operating the ADS5562 ADC down to DC and am looking for a recommended drive input circuitry assuming a 50 ohm source impedance.

  • 0
    TI__Intellectual 1225 points
    Based on the ADC choice of ADS5562 and the desire for DC signals, an initial recommendation would be a fully differential amplifier (FDA) like TI's THS45xx family, specifically the THS4509 or THS4513. 
     
     
    Attached are a couple slides with an overview of the implementation. As shown in the slides, the FDA can convert the single ended source to a differential input for the ADC.
     
    A more detailed recommendation would require more about your requirements, such as
     
    1) Gain needed from amplifier
    2) ADC input swing (this is programmable for the ADS5562, ranging from 3.56V down to ~ 2V)
    3) Signal BW
    4) Power supplies available
    5) Key specifications - Distortion, SNR at what Frequency
     
    If you are planning to use the full range of the ADS5562 with a 3.56V differential swing, then the FDA would likely need a positive and negative supply (e.g. 4V and -1 or -1.5V) to accomodate the output voltage, as it would be too near the lower rail.
    THS4509 ADC Interface.pdf