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  1. With respect to the following 555 timer circuit what will be the value of RA and R such that the LED turns on for a duration of 10 ms every time it receives negative trigger pulse. LED operating current = 20 mA, Vf = 1.4 V, Vo on = 13.4 V and C = 0.22 nf

  2. A.
    41.4 KΩ, 600 Ω
    B.
    45 KΩ, 630 Ω
    C.
    43.5 KΩ, 580 Ω
    D.
    44.9 KΩ, 600 Ω

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    Answer : Option A

    Explanation :

    Timer operated in mono, mode

    RAC =

    RA = 41.4 KΩ

    R = = 600 Ω.


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