Here is the comparison between a ring counter and a Johnson counter:

## Ring Counter:

The output of the last flip-flop is connected back as the input to the starting flip-flop.

The number of states in the ring counter is equal to the number of flip-flops used.

The input frequency of the ring counter is ‘n’.

The output frequency of the ring counter is ‘f/n’, where ‘f’ represents the input frequency.

The total number of unused states in the ring counter is calculated as (2n – n), resulting in (n) unused states.

## Johnson Counter:

The output of the last flip-flop is complemented and given as the input to the starting flip-flop.

The number of states in the Johnson counter is double the number of flip-flops used, resulting in ‘2n’ states.

The input frequency of the Johnson counter is ‘f’.

The output frequency of the Johnson counter is ‘f/2n’.

The total number of unused states in the Johnson counter is (2n – 2n), which means there are no unused states.

In summary, the key differences between the ring counter and the Johnson counter lie in the feedback connections, the number of states, input/output frequencies, and the presence of unused states.

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