555 output to JK flip flop

Discussion in 'General Electronics Chat' started by mbohuntr, Sep 27, 2010.

  1. mbohuntr

    Thread Starter Active Member

    Apr 6, 2009
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    Afternoon... I am still working on my trigger project. Here's a question...If I power the 555 with 5v, 6mA, the output current isn't shown??? so... if the JK flip flop inputmax high current (J,K ,pre) is around 20uA, shouldn't I be placing a 250k resistor in line between them?:confused: Thanks.
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    Not a problem. The logic inputs are really level sensitive. Seeing +5 volts from a 1 ma capable source is the same as +5 from a 100 amp source.
     
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  3. mbohuntr

    Thread Starter Active Member

    Apr 6, 2009
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    Good point! What condition would cause the JK input to exceed 20uA? Perhaps driving something with the "Q" output? Thanks for the help!
     
    Last edited: Sep 27, 2010
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    Not even that - the input structure limits the current. The IC as a whole might draw more current with loads on the output, but not the inputs.
     
  5. mbohuntr

    Thread Starter Active Member

    Apr 6, 2009
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    Thank you!
     
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