Possible application for the circuit on my avatar?

Discussion in 'General Electronics Chat' started by Alexander Angelov, Jul 15, 2015.

  1. Alexander Angelov

    Thread Starter New Member

    Jul 15, 2015
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    It is a JK flip-flop, but I have no idea what it would actually do in a circuit... Possibly drive the output/input in some forced way? -> When bot J and K are 1, Q would toggle, but then J and K would toggle...?
     
  2. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    The answer to you question is simple. The problem is that your drawing is not a good question.

    1. As shown, the circuit will do nothing because there is no clock input.

    2. The short signal line going off the left edge of the image implies that there is an external signal source driving it. That is a conflict with the Q output driving it, so even if there were a clock input the circuit's operation would depend on which of two sources overpowered the other. That kind of source conflict usually ends in device failure.

    3. The J-K flip-flop is defined with both inputs having the same logic polarity. Your drawing shows an inverted K input, which is not available as a purchased component. If you mean that there is an inverter between the Q output and the K input, draw that. If you mean something different, draw that.

    Fix the drawing, go to Wikipedia, get the answer.

    ak
     
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  3. dl324

    Distinguished Member

    Mar 30, 2015
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    It's a JK latch, not a flip flop. As connected, it's useless.
    jkLatchTable.jpg
    It will be reset when power is applied and then do nothing.
     
  4. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Sounds like most of my circuits.
     
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  5. Alexander Angelov

    Thread Starter New Member

    Jul 15, 2015
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    It is not my drawing, it was given to me and it seemed wrong, as you stated, so I wanted to ask other people to see if I'm missing something :)
     
  6. Alexander Angelov

    Thread Starter New Member

    Jul 15, 2015
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    As far as I know, the inverted input at K means that the reset is active low, but who knows... As I said in my previous comment, it was given to me, I was just hoping that other people would be able to make some sense of it.
     
  7. AnalogKid

    Distinguished Member

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    K is not the reset input, it is the K input. Usually the reset input is in the center of the bottom side, marked R. This input can have an inverting bubble or not.

    ak
     
  8. crutschow

    Expert

    Mar 14, 2008
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    There are some FFs (such as the 74109 and 74276) that have an inverted K input so that you can connect the J/K together and it will act as a D FF.
    The OP's circuit could then act as a toggle with a clock input if the J/K inputs were connected to the /Q output.
     
  9. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    I once had an interesting morning with a design engineerning manager who shared the same opinion despite my frequent question of "but what MAKES the circuit reset?" After several rounds of this he stormed off to get one of his staff to back his opinion.

    To his dismay his minion's first question to him was "but what MAKES the circuit reset?"
     
  10. dl324

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    Mar 30, 2015
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    I took the bubble on the K input to mean that it was LOW active instead of the typical HIGH.

    Still not likely to be a useful circuit because J would have to be driven by something and having the Q output connected to J could create a conflict.
     
  11. dl324

    Distinguished Member

    Mar 30, 2015
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    You're right, I didn't take the invert on K into consideration when Q initialized HIGH; that's what I get for trying to do it without drawing a truth table... The circuit has a 50/50 chance of initializing to LOW or HIGH. In either case, equally useless.

    A JK latch would initialize to LOW with Q tied to both inputs...
     
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