Inverters in fiber optic transmitter

Discussion in 'General Electronics Chat' started by Razor Concepts, Apr 27, 2011.

  1. Razor Concepts

    Thread Starter Active Member

    Oct 7, 2008
    212
    1
    In a fiber optic development kit, the schematic for the input to drive the LED is a bit puzzling to me. What is the purpose of the arrangement of inverters after the input? U1 is a 4069 and Q1 is a 3904.
    http://i55.tinypic.com/2u44pax.jpg
    [​IMG]
     
  2. ifixit

    Distinguished Member

    Nov 20, 2008
    638
    108
    Hi Razor Concepts,

    The device driving the input cannot drive the transistor directly so the the circuit designer added two CMOS logic inverters in parallel to get enough drive for the transistor. The buffer next to the input un-inverts the signal and presents only one CMOS load to the device driving the input.

    Regards,
    Ifixit
     
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