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Very high speed Log Amplifiers

Shyam
Expert 1960 points

Other Parts Discussed in Thread: LOG114

My objective :

converting laser pulses from photo diode ranging from 10nA - 100mA (70dB dynamic range of incident power) to digital format, for measuring pulse width exactly

pulse width 10ns and repeating at a rate of 20us

i have seen pretty encouraging application notes for a wide dynamic range TIA requirements of about 100dB input power , but my doubt is how fast they can be ?, as the normal diodes cant be very fast as 2ns(considering my photo diode rise time), how about a Ghz BJT as feedback element or a schottky diode in feedback( i did not find people trying such), i do have found few integrated designs like LOG114 but i did not find a high freq log amplifier modules being available, is it possible to sense ns pulses using log amplifiers ?

  • 0
    TI__Genius 13935 points
    Hello Daram,

    Thanks for your interest in TI parts. I don't have an answer for your question at this time. I will refer your question to our transimpedance expert and see if we can find a solution for you.

    Regards,
    Loren
  • 0
    TI__Genius 12631 points
    Daram,
    We don't have any high-speed log-amps other than the one you already found. I am not sure about using a schottky diode in the feedback but using a discrete high-speed BJT with an fT in the GHz region along with one of the very high speed opamps from our portfolio is certainly something worth trying. Our high-speed amplifier team does not have any product offerings when it comes to discrete transistors however if you find a transistor you like you could simulate it in TINA to see if you can achieve the desired performance.
    -Samir