What is JK flip flop? With circuit diagram and truth table

JK flip flop is the most commonly used flip flop. It is used in various digital circuits, such as registers and counters.

The interesting thing about the JK flip-flop is it can toggle when a HIGH signal is given to both input J and K.

In this post, we make JK flip flop using NAND gates.

Circuit Diagram


Here, we connect the output Q to the below AND gate. Similarly, connect Q' to the upper AND gate.

If the clock is LOW, the JK flip flop will be in a memory state. It means the output of the JK flip flop will be the same as before and there will be no changes in output.

Truth Table for JK flip flop

From the above circuit diagram, we can see that the JK flip-flop is symmetrical. When power is supplied to the circuit, either Q or Q' can be HIGH at a time.

So we consider Q=1 and Q'=0. You can consider any values but both values should not be the same.


When Q=1, it is called SET state.

Similarly, when Q=0, it is called a RESET state.

If you look at the pattern, you can see that the output is similar to input J and K except when both J and K are HIGH.


JK flip-flops are used in various digital electronics gadgets. Unlike other flip-flops, it doesn't have any invalid states.

JK flip-flops are not suitable for higher frequency applications because with a single HIGH clock pulse, it can toggle many times. In that case, it is very hard to predict the next state.

If you need to design high-frequency circuits you can replace the JK flip-flop with a Master JK flip-flop.


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