Q- Design MOD-3 ripple counter using (a) Observing outputs (b) K-maps to design the circuit.
Ans: (a)We can design the MOD 3 counter using 2 FFs as 3 is less than 4 i.e. 22 and greater than 2. We can see directly that as we have to reset the counter only after 2 i.e. when output is 3 we reset the counter and hence we need to reset only when we have Q0= 1 & Q1=1. Now firstly design MOD-4 counter using 2 FFs and then take NAND of Q0 & Q1 and feed the output to CLEAR of both FFs.
(b) We firstly draw state diagram of the counter required as:
And we have the general circuit to design the other than MOD 2 n then we have the general circuit as
And now we draw a table to list the different input combinations to Combinational circuit and their corresponding output as:
Q1 Q0 OUTPUT of reset logic
0 0 1
0 1 1
1 0 1
1 1 0
And using K-map as
And hence we get the whole circuit for MOD-3 counter as