Regarding jk flip flop Q' stability.

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SUMMARY

The discussion focuses on the stability of the Q' output in JK flip-flops, particularly when using RS flip-flops constructed with NOR gates. The user observed that Q' oscillates between 0 and 1 when Q is set to 1, J to 1, and K to 0, while Q settles to 1. It was clarified that Q' does not oscillate under these conditions due to the behavior of the AND gates involved. The oscillation issue arises when both J and K are set to 1, especially if the clock enable time exceeds the R/S delay, which can be resolved by implementing a master-slave JK flip-flop.

PREREQUISITES
  • Understanding of JK flip-flop operation
  • Knowledge of RS flip-flops using NOR gates
  • Familiarity with characteristic tables of flip-flops
  • Concept of master-slave flip-flop configurations
NEXT STEPS
  • Study the operation and timing diagrams of JK flip-flops
  • Learn about master-slave JK flip-flop designs
  • Investigate the effects of clock enable time on flip-flop stability
  • Explore characteristic tables for various types of flip-flops, including D and T flip-flops
USEFUL FOR

Electronics engineers, digital circuit designers, and students studying sequential logic circuits will benefit from this discussion.

nascentmind
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Hi,

I am trying to understand and analyze JK flip flop's (using RS flop flop i.e. using NOR gates). I have written out the characteristic table and when I give Q = 1, J=1 and K = 0 I am trying to analyze the Q' (Q complement) by giving the intial state to 0. I find that Q settles to 1 (i.e. Q(t+1)) but Q' oscillates between 0 and 1. How is this fixed? Is the Q' needed in JK flip flops? Also why do textbooks don't talk about Q' in JK or D or T but only Q and Q(t+1) ?

Thanks.
 
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No it won't oscillate for Q=1, J=1, K=0. AND gate with i/p K will always be 0 and AND gate with i/p Q' will always be 0, making FF to hold its state.

However, for J=1, K=1, If the clock enable time is larger than Q/Q' to R/S delay the circuit will oscillate. To resolve the problem use master slave JK FF.
 

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