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Difference between high precision and high speed DAC related with AD9744 and LTC1668

Category: Hardware
Product Number: ltc1668 and ad9744


I am little bit confused with difference between high precision and high speed DAC definitions.

In my application I will drive some DC level continuously as above but I have to generate these DCs without much noise.

What do you offer for selection of DAC?  What would be your choice between LTC1668 or AD9747. Are there any suggestion for different DAC selection.


Top Replies

  • Hi  ,

    As I understand it, the main difference between High precision and High-speed DACs is in the frequency of interest as they apply to different applications. High precision DACs provide accuracy and clean code transition in the lower end of the spectrum (DC to hundreds of kHz, sometimes tens of MHz). Precision DACs requires an output signal with absolute accuracy. Also, total noise power is accumulated in these devices thus bandwidth is kept small to keep the noise small. 

    On the other hand, High-speed DACs provide spectral cleanliness or coherency of samples in a passband that is hundreds of MHz to several GHz. These devices typically take advantage of the de/modulation process, so only noise within the bandwidth of the device is considered. Because coherency of samples is the key factor, these DACs are required to produce a signal with good accuracy, but not necessarily absolute. For these devices, the noise spectral density (NSD) in the band of interest is kept as low as possible. More details can be found here: Fast Precision DACs versus High-Speed DACs.

    Because you're operating at the lower end of the spectrum, it might be better to go for Precision DACs. I also think you must use an external amplifier to achieve the 2-3V output since LTC1668 has only up to 10mA FSC (full-scale current), while AD9747 is up to 31.7mA FSC. Other DAC selections can be found here: D/A Converters (PST).



  • Hi Erdogdu,

    Based from your diagram, you want your update rate at around 500kHz.

    I suggest you proceed using LTC1668 as this have performance data showing for output of 500kHz at 5MSPS.

    Best regards,

  • Thanks for your reply JMMina. I am between two different amplifiers for amplification stage of DAC.

    ADA4927-1 or LTC6409. I am little bit confused with selection of amplification stage. Do you suggest one of these or any others differential amplifier for my application.

    Thanks for your reply Peevee. Do you have any other DAC suggestions for this application?


  • Hi  ,

    If you will use the LTC1668, there are companion products for amplifiers in page 24 of the LTC1668 Datasheet as well as in the LTC1668 Product page under the Evaluation Kits section. Other low-noise op-amps (≤ 10nV/√Hz) can be found here.