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PIN photodiode & TIA question

Discussion in 'Electronic Design' started by Roman D. Sinjuk, Sep 17, 2005.

  1. Hi everybody.

    I am going to use S7481 photodiode as high speed photodetector for 100Mbit/s
    free space optical link. It is high speed photodiode (Cut-off frequency 500MHz)
    with high sensitivity in visible range (http://jp.hamamatsu.com/resources/products/ssd/pdf/s6431_etc_kpin1018j03.pdf),
    but it has high junction capacitance - 6pF. I have MAX3657 transimpedance
    amplifier (TIA) (http://pdfserv.maxim-ic.com/en/ds/MAX3657.pdf).
    But it optimized for 0.5pF capacitance photodiodes. For 0.5pF MAX3657 has
    130MHz signal bandwidth, for 1.5pF bandwidth is 50MHz. It less than 75Mhz,
    needed for 100Mbit/s. Not only bandwidth decreased, input referred noise level
    increase also.

    Can I loss sensitivity but reach 75Mhz bandwidth on S7481 + MAX3657?
    Or I need other solution ? What would you recommend ?
     
  2. Phil Hobbs

    Phil Hobbs Guest

    I have an article on my web site that has this, with detailed design steps.

    http://www.pergamos.net, about halfway down.

    Cheers,

    Phil Hobbs
     
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