### MOD 4 Synchronous Counter using JK Flip-flop

Here you will see how to design a MOD-4 Synchronous Counter using JK Flip-flop step by step.

## MOD 4 Synchronous Counter using JK Flip-flop

### Step 1: Find the number of Flip-flops needed

The number of Flip-flops  required can be determined by using the following equation:

M ≤ 2

where, M is the MOD number and N is the number of required flip-flops.

Here, MOD number is equal to 4. i.e., M = 4

Therefore, 4 ≤ 2

=> N = 2

### Step 2: Write the excitation table of the flip-flop

Excitation table of JK flip-flop is:

 QN QN+1 J K 0 0 0 X 0 1 1 X 1 0 X 1 1 1 X 0

### Step 3: Write the circuit state table by using excitation table

Circuit state table for designing MOD 4 Synchronous Counter using JK Flip-flop would be

 QA QB QA+1 QB+1 JA KA JB KB 0 0 0 1 0 X 1 X 0 1 1 0 1 X X 1 1 0 1 1 X 0 1 X 1 1 0 0 X 1 X 1

### Step 4: Prepare K Map for each flip-flop input in terms of flip-flop outputs as the input variables

In this case inputs of the flip-flops are:  JA, KA, JB & K

K Map for JA :

Therefore,  JA =  QB

K Map for K:

Therefore, KA = QB

K Map for JB :

Therefore, JB = 1

K Map for KB :

Therefore, KB = 1

### Step 5: Draw the circuit using flip-flops and other gates correspond to the minimized expressions

Circuit for MOD 4 Synchronous Counter using JK Flip-flop would be

In this way "MOD 4 Synchronous Counter using JK Flip-flop" can be designed.