Verify the truth table of a J-K flip-flop (7476)

Jun 25 2023

Aim

Apparatus Required:

Logic trainer kit, Flip-flop ICs- 7476, wires.

Truth table:

Q	J	K	Q(t+1)
0	0	0	0
0	0	1	0
0	1	0	1
0	1	1	1
1	0	0	1
1	0	1	0
1	1	0	1
1	1	1	0

The flip-flop is constructed in such a way that the output Q is ANDed with K and CP. This arrangement is made so that the flip-flop is cleared during a clock pulse only if Q was previously 1. Similarly, Q’ is ANDed with J and CP, so that the flip-flop is cleared during a clock pulse only if Q’ was previously 1.

When J = K = 0When both J and K are 0, the clock pulse has no effect on the output and the output of the flip-flop is the same as its previous value. This is because when both the J and K are 0, the output of their respective AND gate becomes 0.

When J=0, K=1When J=0, the output of the AND gate corresponding to J becomes 0 (i.e.) S=0 and R=1. Therefore, Q’ becomes 0. This condition will reset the flip-flop. This represents the RESET state of Flip-flop.

When J=1, K=0In this case, the AND gate corresponding to K becomes 0(i.e.) S=1 and R=0. Therefore, Q becomes 0. This condition will set the Flip-flop. This represents the SET state of Flip-flop.

When J=K=1Consider the condition of CP=1 and J=K=1. This will cause the output to complement again and again. This complement operation continues until the Clock pulse goes back to 0. Since this condition is undesirable, we have to find a way to eliminate this condition. This undesirable behavior can be eliminated by Edge triggering of JK flip- flop or by using master slave JK Flip-flops.