The document explains the JK flip-flop, a type of sequential logic circuit that is a modification of the SR flip-flop, eliminating invalid states. It serves as a universal programmable flip-flop, where the J and K inputs behave as set and reset inputs, with toggling behavior dependent on clock signals. Additionally, it addresses issues such as the race around condition and methods to prevent it, including using edge triggering in a master-slave configuration.

1. JK Flip-Flop

2. Today's Topic
Sequential Logic Circuits
• JK Flip-Flop

3. Why JK Flip-Flop
• SR
• D

4. J K Flip-Flop
• JK flip – flop is named after Jack Kilby, the electrical engineer who
invented IC.
• A JK flip – flop is called a Universal Programmable flip – flop
because, using its inputs J (Preset), K (Clear), function of any other
flip – flop can be imitated.
• It is the modification of SR flip – flop with no Invalid state.

5. JK Flip-Flop
• In this the J input is similar to the SET input of SR flip – flop and
the K input is similar to the RESET input
• And outputs are
– one is main output represented by Q and
– the other is complement of Q represented by Q’.
• The symbol of JK flip – flop is shown below.

6. Construction & Logic Circuit
JK Flip-Flop Using NOR gates
JK Flip-Flop Using NAND gates

7. NAND Truth table
1. J=0 , K=1 Q=0 Q’=1
2. J=0 , K=0 Q= 0 Q’= 1
3. J=1 , K=0 Q= 1 Q’= 0
4. J=0 , K=0 Q= 1 Q’= 0
5. J=1 , K=1 Q= T Q’= T
A B Y
0 0 1
0 1 1
1 0 1
1 1 0

8. Clk J K Q Q’ State
↑ » 1 0 0 Q Q’ NC
↑ » 1 0 1 0 1 RESET
↑ » 1 1 0 1 0 SET
↑ » 1 1 1 T T Toggle
» 0 X X - - -
JK Flip-Flop Truth Table

9. Clk J K Q(t) Q(t+1) State
↑ » 1 0 0 0 0
Memory / No change state
↑ » 1 0 0 1 1
↑ » 1 0 1 0 0
RESET
↑ » 1 0 1 1 0
↑ » 1 1 0 0 1
SET
↑ » 1 1 0 1 1
↑ » 1 1 1 0 1 0 1 0..
Toggle
↑ » 1 1 1 1 0 1 0 1..
JK Flip-Flop Characteristic Table
 Toggle means switch between two states.
 Conditions for toggle in JK- flip flop :
 Both J and K should be 1.
 Clock should be present( Here I have considered +ve clock/rising edge)

10. Timing Diagram

11. Review
• A J-K flip-flop is nothing more than an S-R flip-flop with an added layer
of feedback.
• This eliminates the invalid condition.
• When both J and K inputs are activated (J=1,K=1), and the clock input
is applied then the circuit will toggle from a set state to a reset state or
vice versa.
• The limitation of JK Latch is Race Around Condition (in JK Latch)
 Race around condition means toggling is happening at the output many
a time within a single clock period.

12. Steps to avoid racing condition
• We can avoid the Race around condition by setting up the clock-on time
less than the propagation delay of the flip flop. It can be achieved by edge
triggering.
• By making the flip flop to toggle over one clock period.
This concept is introduced in Master Slave J K flip flop.

13. In Next Class
• Master Slave JK Flip Flop

14. • A