Suitable adc bits/speed for photodiode

Discussion in 'General Electronics Chat' started by Vindhyachal Takniki, Apr 24, 2015.

  1. Vindhyachal Takniki

    Thread Starter Member

    Nov 3, 2014
    1. I have to design transimpedence amplifier(TIA) for monitoring photodiode in Fiber Coupled Diode Lasers.
    2. Opamp which i will use for TIA is MCP6491 , 3.3V powered.
    3. The input pulse for laser diode will be approx 1us.
    4. Now as far as I understand, this is time when photodiode will give ouput? (I don't know just a guess, don't understand how this pair works).
    5. If yes, then what speed/bits of adc should I choose.
    6. Any AN or website link for understanding the operation.
    7. The link that I have read are either of photodiode or laser. Don't know how this combination works or what will be output of photodiode when laser turns on?
  2. RichardO

    Well-Known Member

    May 4, 2013
    1. OK.
    2. I don't think your op-amp is any where near fast enough for a 1 us pulse.
    3. and 4. Sounds right to me.
    5. The speed has to be fast enough to do an entire A/D conversion in 1 us. To be more precise, the conversion must start after the Laser pulse is detected and end before the pulse goes away. How many bits do you think you need and why?
    6. and 7. Google is your friend.