## What is JK Flip Flop?

JK flip flop is a refined and improved version of the SR flip flop that has been introduced for solving the problem of indeterminate state that occurs in SR flip flop when both the inputs are 1.

In JK flip flop,

• Input J behaves like input S of SR flip flop which was meant to set the the flip flop.
• Input K behaves like input R of SR flip flop which was meant to reset the the flip flop.

## Difference between JK Flip Flop and SR Flip Flop-

Functionally, both JK flip flop and SR flip flop are same with only one difference.

The only difference between SR flip flop and JK flip flop is that in JK flip flop, indeterminate state does not occur.

Instead of indeterminate state, in JK flip flop, the present state toggles i.e. the present state gets inverted when both the inputs are 1.

## Construction of JK Flip Flop-

JK flip flop can be constructed in two ways-

1. By using SR flip flop constructed using NOR latch
2. By using SR flip flop constructed using NAND latch

 RememberJK Flip Flop = SR Flip Flop + 2 other connections

### Way-01: Construction of JK Flip Flop by using SR Flip Flop constructed using NOR latch-

Here, we use SR flip flop constructed using NOR latch and two other connections to construct the JK flip flop.

### Logic Circuit- ### Way-02: Construction of JK Flip Flop by using SR Flip Flop constructed using NAND latch-

Here, we use SR flip flop constructed using NAND latch and two other connections to construct the JK flip flop.

### Logic Circuit- ### Logic Symbol- ### Truth Table-

 INPUTS OUTPUTS J K Qn (Present State) Qn+1 (Next State) 0 0 0 0 0 0 1 1 0 1 0 0 0 1 1 0 1 0 0 1 1 0 1 1 1 1 0 1 1 1 1 0

The above table can be reduced as-

 INPUTS OUTPUTS REMARKS J K Qn (Present State) Qn+1 (Next State) States and Conditions 0 0 X Qn Hold State condition J = K = 0 0 1 X 0 Reset state condition J = 0 , K = 1 1 0 X 1 Set state condition J = 1 , K = 0 1 1 X Q’n Toggle state condition J = K = 1

### Characteristic Equation-

Draw a k map using above truth table- Qn+1 = Q’n (JK + JK’) + Qn (J’K’ + JK’)

 Qn+1 = Q’nJ + QnK’

### Excitation Table-

We will draw excitation table of any flip flop using its truth table.

 What is excitation table?For a particular combination of present state Qn and next state Qn+1, excitation table tell the inputs required.

 Qn Qn+1 S R 0 0 0 X 0 1 1 X 1 0 X 1 1 1 X 0

Get more notes and other study material of Digital Electronics.

Watch video lectures by visiting our YouTube channel LearnVidFun.