Sequential Logic Circuits

Sequential logic circuits differ from combinatorial logic circuits in two main respects.

• The output of the system depends not only on the present external input(s) but on the previous inputs also
• The same external input(s) can give a different output response.

An important feature of sequential logical circuits, not present in combinatorial logic circuits, is the presence of feedback where the output from one or more logic gates is fed back into the input(s) of logic gates further back in the circuit.