Sequential circuits are circuits that store and use previous state information to determine their next state. Unlike combinational circuits, which only depend on current inputs, sequential circuits rely on both current inputs and the previous state stored in memory elements, typically implemented using flip-flops

There are two main types of sequential circuits:

  1. Asynchronous sequential circuits: These do not use clock signals and respond immediately to input changes. They are faster but more challenging to design

  2. Synchronous sequential circuits: These use clock signals to synchronize state changes. They are more common and easier to design, though slightly slower than asynchronous circuits

Example: Serial Adder, Instruction Pipeline