Sequential Circuit

Sequential Circuit

The combinational circuit does not use any memory, hence the previous state of input
does not have any effect on the present state of the circuit. Their output values are
computed entirely from their present input values.
The sequential circuit has memory so output can vary based on input. This type of
circuits uses previous input, output, clock and a memory element.
In sequential circuits, memory elements are added to combinational circuits to form a
feedback path. The memory elements are devices capable of storing binary information
within them. This information defines the state of the sequential circuits. Since
memory is finite, therefore, the sequence size must always be finite, which means that
the sequential logic can contain only a finite number of states. So sequential circuits
are sometimes called finite-state machines. The sequential circuit receives binary
information from external inputs. The inputs, together with present state determine
the binary value at output terminal. The sequential circuit is specified by a time
sequence of inputs, outputs and internal states.
“The sequential circuit is a circuit whose output depends on the present inputs as well
as on past outputs.”
Block diagram

Characteristics of Sequential Circuit:

1. It is a circuit which works in sequence by taking present inputs and past value of inputs.

2. It contains at least one memory element for storage of previous outputs.

3. In this output is fed as input directly or indirectly.

4. It becomes complex to design due to presence of memory element.

5. Its performance depends on the set of subsequent state values and set of output values.

6. It is comparatively slower in speed as output is delayed.

7. It requires less hardware for its realization

8. It is cheaper in cost because of less hardware.