Describe the operation of a Johnson counter.

A Johnson counter, also known as a twisted-ring counter, is a type of digital sequential circuit that produces a cyclic sequence of states. It is essentially a shift register with feedback from the last bit to the first, creating a loop.

Here’s how a Johnson counter operates:

Initialization: Initially, all the flip-flops (or stages) in the Johnson counter are reset to a known state, typically all zeros.

Clocking: On each clock pulse, the contents of the counter shift one position to the right (or left), similar to a shift register. The shifting direction depends on the design of the counter.

Feedback: In a Johnson counter, the output of the last flip-flop is fed back to the input of the first flip-flop. This creates a loop, allowing the counter to cycle through a sequence of states.

Sequence Generation: As the counter shifts, the states of the flip-flops represent different binary values. The sequence of these values forms the output sequence of the Johnson counter.

Cycle Completion: The counter continues to shift and cycle through its states indefinitely. The length of the sequence generated by the Johnson counter depends on the number of flip-flops used in the counter. For

n flip-flops, the counter can generate a sequence of length 2^n

.

Applications: Johnson counters find applications in various areas such as frequency dividers, sequence generators, and frequency synthesis circuits.