Definition of Sequential Circuit

Unlike a combinational circuit which operates solely based on the present, a sequential stores and processes digital information in a sequential manner i.e. it has an additional element called memory which enables it to consider not only the present but also the past inputs or states. This memory element plays a vital role as it enables the processing of streams of data.

As shown in the above figure, there are two types of input to the combinational logic : 

• External inputs which are not controlled by the circuit.
• Internal inputs, which are a function of a previous output state.

Examples of Sequential Circuits:

Sequential circuits are used to develop various building units which are discussed below:

• Flip-Flops: A flipflop is used as a memory element to store bitwise binary information(0 and 1 only). Flipflops are the main form of sequential circuit where two stable states(set and reset) are working sequentially based on trigger condition(known as clock pulse).
• Counters: Counters are specially designed sequential circuits which are simply used for counting pulses or events or various sequences like binary, decimal or Gray code etc. Counters can be found in digital clocks, frequency dividers etc.
• Shift Registers: Shift registers are nothing but chain of multiple flipflops which are connected to each other serially to store and shift data serially. It listens to the clock pulses to decide to perform shifting operation. Shift registers are used in data storage and communication system and parallel-to-serial(P2S) or serial-to-parallel(S2P) conversion systems.

A sequential circuit is widely used for storing and processing information such as retaining and manipulating data which makes them an essential component in various electronic devices in the realm of digital electronics. Sequential circuits process data in a sequential manner which makes them essential building blocks of many applications computer processors, memory systems, and communication networks by enabling memory retention and feedback capabilities.