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High Speed OPAM amplifier

krishna dayal shukla
Prodigy 60 points

Other Parts Discussed in Thread: LMH6629, OPA847

Hi 

In my experiment I want to amplify a 1uV pulse  ( 1ns rise time/ fall time and 1.5 ns pulse width) up to 5 mV without adding  any noise, delay and distortion.Kindly suggest me a better  IC that can do this job.

Regards

Krishna D Shukla 

  • 0
    TI__Genius 12631 points

    Hello Krishna,

       If you need a single amp to do this, you will need a BW of 0.35/1ns = 350MHz and a gain of 5mV/1uV = 5000. This is a Gain Bandwidth Product of 1.75THz. There are no amps any where close to this kind of performance. Also, from a noise persepective you need an amplifier with an input referred noise many decades below what is currently available. Our highest BW, lowest noise amplifiers are the OPA847 and LMH6629, but their performance is nowhere close to what is needed for your application.

    Samir

  • 0 in reply to Samir Cherian
    Prodigy 60 points

    Thank you Samir

    The amplification may go for multiple stages but noise and speed should be in desired range. kindly suggest any circuit design or OPAM IC.
    Krishna
  • 0 in reply to krishna dayal shukla
    TI__Genius 12631 points

    Hello Krishna,

      If we use the LMH6629 amplifier which has a BW of 1GHz with a gain of 10. This corresponds to about a gain of 25 for a 400MHz BW. Now the integrated RMS noise will be 0.69nV/rtHz * sqrt(400MHz) = 13.8uV. This is above your 1uV input signal so I am afraid it will be drowned out. One way to reduce the noise is to kill the BW of the amplifier with some filtering, however that would then cause distortion. There is no straight solution to your problem, you will have to decide which parameters you are willing to sacrifice and by how much. You can use TINA spice to simulate and play with your various options. TINA is avaiable for free download from the TI website.

    http://www.ti.com/tool/tina-ti?keyMatch=TINA&tisearch=Search-EN

    Samir