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ADS4242: Ads4242

Yinon Kares
Prodigy 60 points
Part Number: ADS4242
Hi, I work with ads4242 as a final stage in my rf cascade. I want to get a low noise figure and therefore try to get A high gain in low NF such that ADC NF contribution to Overall NF will be small. I try to understand if using 1:N (and not 1:1) transformer as balun (can help in reduce the required cascade gain to such purpose (voltage gain) ? This is for reduce power gain (and get more linearity) Thanks, Yinon
  • 0
    TI__Guru* 91947 points

    Yinon,

    Yes, using a 1:N transformer will allow you to increase the signal swing without adding noise as this is a passive device. You will need to be careful when choosing a transformer as the linearity will vary from model to model. I have attached a couple of documents that may be of use as well.

    Regards,

    Jim

    Fundamentals of High Speed ADC Nov 2012.pptTransformers.ppt

  • 0 in reply to jim s
    Prodigy 60 points
    Hi him, I understand the voltage gain witch achieved without adding noise. I try to understand if it will help me in aspect of noise figure. Assume that we speak on 10 dbm full scale of the ADC and ADC SNR of 70 dbm - the ADC noise is -60 dbm. It’s a high NF...I want to reduce the overall NF by channel noise over gain. Because transformer save energy I get a contribution from the 1:N ratio in get smaller ADC noise figure contribution to overall cascade NF (like in use LNA for example) ? Best regards, Yinon
  • 0 in reply to Yinon Kares
    TI__Guru* 91947 points

    Yinon,

    I am confused about your reply. Are you planning on running the input at 10dbm of full scale? If so, what is this in p-p voltage? Do you then plan on gaining up this input to a higher scale? You mention SNR 70 dbm - ADC noise is -60dbm? Is this a measurement from your system? Are you referencing any tables or figures from the data sheet? What do you mean by reducing overall NF channel noise over gain? Are you asking for suggestions on how to reduce noise when adding gain, if possible?

    Regards,

    Jim