This type of system uses storage elements called flip-flops that are employed to change their binary value only at discrete instants of time. Because of the feedback among logic gates, the system may, at times, become unstable. Gate-type asynchronous systems are basically combinational circuits with feedback paths. This is a system whose outputs depend upon the order in which its input variables change and can be affected at any instant of time. Their classification depends on the timing of their signals: There are two types of sequential circuits. A sequential circuit is specified by a time sequence of inputs, outputs, and internal states. Memory elements next state is also a function of external inputs and present state. The input and the present state of the memory element determines the output. The binary info stored in the memory elements at any given time defines the state of the sequential circuit. The memory elements are devices capable of storing binary info. Combinational logic output depends on the inputs levels, whereas sequential logic output depends on stored levels and also the input levels. So, the memory element is not required, In a sequential circuit the output depends upon both present input and present state, so the memory element is required to save the feedback state.Digital electronics is classified into combinational logic and sequential logic. Combinational circuits the output depends only upon the present input and there is no need for feedback for input and output.Combinational circuits are faster logic circuits while sequential circuits are slower than combinational circuits.In the combinational circuit, elementary building blocks are only logic gates, while the sequential circuit element building blocks are flip-flops.In combinational circuit clock signal are not required and it is not dependent on time, while the sequential circuit clock signal is required and it is dependent on time and clock so need triggering.The combinational circuit is easier to design, use and handle, while a sequential circuit is not easier to design, used, and handle than the combinational circuit.Sequential circuits are the type of circuit where output not only relies on the current input but also depends on the previous output.ĭifference between combinational circuit and sequential circuits:
The combinational circuit is the type of circuit in which the output is independent of time and only relies on the input present at that particular instant. So here this article gives the main key difference between combinational circuits and sequential circuits. These are two broad categories of circuits defined in digital electronics where one type of circuit is independent of time and the other is dependent on time. In digital electronics, both combinational circuits and sequential circuits are the most widely used circuits.
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