fan out of 74ALSO4

Discussion in 'General Electronics Chat' started by muni, Sep 2, 2008.

  1. muni

    Thread Starter Active Member

    Jul 29, 2008
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    QUESTION FROM GATE PAPER AGAIN. REQUEST ANSWER

    the inverter 74 ALSO4 has the following specifications.
    IOh max = -0.4 mAmp,
    IOL max = 8 mAmp
    IiH max = 20 mAmp
    IiL max = -0.1 mAmp


    Calculate fan out based on the above will be
    a) 10 b) 20 c) 60 d) 100

    i request how to calculate the fan out, though book gives answer but my request is how to calculate this.

    SIR I ALSO REQUEST HOW TO UPLOAD MY FILE THAT IS AVAILABLE IN MY PC. I TRIED THROUGH ATTACHMENT I COULDN'T DO IT. PLEASE TELL ME HOW TO ATTAACH FILE INTO THE FORUM

    THANK YOU
     
    Last edited: Sep 2, 2008
  2. mik3

    Senior Member

    Feb 4, 2008
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    There is an error in yuor values, the input current is greater than the output current, i think it should be in uA rather than mA.
     
  3. muni

    Thread Starter Active Member

    Jul 29, 2008
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    sir in that case plase consider your own values and can u give me formula how to calculate fan out for this ic
     
  4. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Fanout is defined as the number of inputs an output can drive. Did you Google fanout?
     
  5. muni

    Thread Starter Active Member

    Jul 29, 2008
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    sir i've searched through google i'm getting same threads as searcg results. with wikipedia i'm getting this.

    The fan-out is simply the number of inputs that can be connected to an output before the current required by the inputs exceeds the current that can be delivered by the output while still maintaining correct logic levels. The current figures may be different for the logic zero and logic one states and in that case we must take the pair that give the lower fan-out. This can be expressed mathematically as
    [​IMG] by applying values -0.4 mAmp/ 20 mAmp.
    even then answer doesn't match with any of the choices.

    request for new look
    thank you sir
     
  6. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Show us your calculations.
    The Wikipedia equation includes the floor function. Do you understand what this is?
     
  7. muni

    Thread Starter Active Member

    Jul 29, 2008
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    no sir i haven't seen the floor functions.

    sir i don't know how to upload a file itno the forum else i can show u the calculation. thank you sir . i'm going through floorfunctions
     
  8. muni

    Thread Starter Active Member

    Jul 29, 2008
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    sir i went through floor functions. but hardly i could understnad any thiing. sorry sir.

    in this particular Q there are no calculations to carry on but i think i need right formula to solve it
     
  9. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    IIH max=20uA, not 20mA, as you stated.

    Below is a schematic which illustrates how fanout is calculated.
     
  10. beenthere

    Retired Moderator

    Apr 20, 2004
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    Another factor that makes a firm answer impossible, is that the chip might be driving another logic family (like 74LSxx) and the input requirements will be different, directly affecting fanout.
     
  11. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Don't you think we can assume that the values for IOH, IIH, IOL, and IIL given are intended to bracket the problem? Let's not confuse our OP any more than he/she is already.:D
     
  12. beenthere

    Retired Moderator

    Apr 20, 2004
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    Point taken - I'm just too aware of finding that the book didn't cover quite all the situations....
     
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