21. How many FFs are required to build a binary counter circuit to count from 0 to 1023?

1. 1. 1

   
   
   

   2. 6

   
   
   

   3. 10

   
   
   

   4. 24

   
   
   

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1. View Hint View Answer Discuss in Forum

   Number of FFS required = 2ⁿ = 1024
   ∴ n = 10

   Correct Option: C

   Number of FFS required = 2ⁿ = 1024
   ∴ n = 10

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22. Part of a digital phase meter is shown in the given figure. If input signals are
    V_R (t) = V_R sin ωt
    and V_p(t) = – V_p sin(&omrga;t + 30°), then reading of the meter will be
    
    

1. 1. 30°

   
   
   

   2. 330°

   
   
   

   3. 150°

   
   
   

   4. 210°

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

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23. For the logic circuit shown in the figure, output Y is
    
    

1. 1. A ⊕ B

   
   
   

   2. A ⊕ B

   
   
   

   3. A ⊕ B ⊕ C

   
   
   

   4. none of these

   
   
   

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1. View Hint View Answer Discuss in Forum

   Output is 1 when even parity
   ∴ Y = A ⊕ B ⊕ C
   

   Correct Option: D

   Output is 1 when even parity
   ∴ Y = A ⊕ B ⊕ C
   

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24. A 4 bit ripple counter and a 4 bit synchronous counter are made by flips flops having a propagation delay of 10 ns each. If worst case delay in the ripple counter and the synchronous counter be R and S respectively, then
    

1. 1. R = 10 ns, S = 40 ns

   
   
   

   2. R = 40 ns, S = 10 ns

   
   
   

   3. R = 10 ns, S = 30 ns

   
   
   

   4. R = 30 ns, S = 10 ns

   
   
   

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1. View Hint View Answer Discuss in Forum

   In ripple counter, delay 4T_d = 40 ns.
   If synchronous counter are clocked simultaneously then its worst delay will be equal to 10 ns.
   

   Correct Option: B

   In ripple counter, delay 4T_d = 40 ns.
   If synchronous counter are clocked simultaneously then its worst delay will be equal to 10 ns.
   

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25. The three-stage Johnson counter as shown in figure is clocked at a constant frequency of ƒ_c from the starting state of Q₂Q₁Q₀ = 101. The frequency of output Q₂Q₁Q₀ will be
    
    

1. 1. ƒ_c/8

   
   
   

   2. ƒ_c/6

   
   
   

   3. ƒ_c/3

   
   
   

   4. ƒ_c/2

   
   
   

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1. View Hint View Answer Discuss in Forum

   
   We see that 1 0 1 repeat after every two cycles, hence frequency will be ƒ_c/2 .
   

   Correct Option: D

   
   We see that 1 0 1 repeat after every two cycles, hence frequency will be ƒ_c/2 .
   

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