Help with this DTL circuit!!!!

Discussion in 'Homework Help' started by genta, Dec 1, 2008.

  1. genta

    Thread Starter New Member

    Dec 1, 2008
    2
    0
    Hi!

    can anyone help me about this DTL circuit in the photo below?

    thiis circuit is about finding the minimum HFE value

    Fan-out is = 20 and the other values are in the photo below,there's missing one Rc value and it's the same Rc=1k

    The hfe has to be about 11, hfe=11, but...
    i solved it and I get hfe =7

    what's the problem????

    please HELP!


    [​IMG][​IMG]


     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,157
    1,795
    What assumption are you making about the thresholds for a logic 1 and a logic 0. You need to take into account the beta of the transistor, the base resistance and the collector resistance none of which you have provided.
     
  3. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    Look at the attached schematic.

    EDIT: Hmmm, I probably should have just given some hints. I forgot this was a homework problem.
     
    Last edited: Dec 2, 2008
  4. genta

    Thread Starter New Member

    Dec 1, 2008
    2
    0
    thank you very much Ron!!!!
     
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