why the resistor of 10K used in the circuit ?

Discussion in 'General Electronics Chat' started by arjun2054, Jul 31, 2016.

  1. arjun2054

    Thread Starter New Member

    May 24, 2016
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  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Pull down resistor when the DSW1/2 is off.
    In order to guarantee 0v on XOR input.
    Max.
     
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  3. RichardO

    Well-Known Member

    May 4, 2013
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    Note that pull down resistor works well on CMOS logic but not very well for TTL logic. TTL inputs source current from the 5 volt power supply and this current must not cause a voltage drop of more than 0.4 volts in the pull down resistor. With TTL, a pull _up_ resistor would be used.
     
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