Logic circuits can be Combinational or Sequential.

Combinational Circuits are circuits made up of different types of logic gates. A logic gate is a basic building block of any electronic circuit. The output of the combinational circuit depends on the input present at any given time. The circuits do not make use of any memory or storage device.

Sequential Circuits are designed using logic gates and memory or storage devices. The output of the sequential circuit depends on present input and previous output.

Feedback path is present in sequential circuit, where as no feedback path in combinational circuit.

The design procedure of a combinational circuit is

1) From the specifications of the combinational circuit, identify the number of inputs and number off outputs and assign a symbol to each input and output.

2) Derive the truth table

3) Find the simplified Boolean function of each output as a function of the input variables.

4) Draw the logic diagram according to the simplified Boolean expressions of output variables.

In this course, I have explained the following concepts.

Half adder, Full adder, Parallel adder

Half subtractor, Full subtractor, Parallel subtractor

Decoder, Encoder

Multiplexer, Demultiplexer

Designing larger Multiplexer from smaller Multiplexer

Designing larger DeMultiplexer from smaller DeMultiplexer

Designing larger Decoder from smaller Decoder