Like decoder, the encoder also provides the conversion of binary information from one form to another Encoder performs the opposite function of a decoder. It gives information in a more compact form. The encoder has more input lines than output lines or says output lines are less than the input lines. It has m input lines and n output lines. From m input lines, only one is activated at a time and gives an equivalent code on n output lines. The block diagram of the encoder is shown in fig.1.The encoder is a digital or combinational circuit that converts an active signal into a coded output signal.
Encoders are used to reduce the number of bits needed to represent the given information) A practical use of encoders is for transmitting information in a digital system. Encoding is also useful if the information is to be stored for later use because fewer bits are required to be stored.
Sometimes, digital information represented in binary form must be converted into some other form. This is obtained by multiple inputs-multiple outputs logic circuit known as a decoder. The most commonly used decoder is n to 2m line decoder. The block diagram of (n: m) decoder is shown in fig.1. It has n input lines and m 2 output lines.
In a decoder, m output lines are greater than n input lines. But when input lines are equal to output lines then it is known as a converted. It converts one form of n bit binary information into another form of m bit binary information.
For example BCD to excess-3 code converter, binary to gray code converter etc. In another case when m output lines are less than 2n then this type of decoder is known as function specific decoder. For example, BCD to decimal decoder, BCD to seven segment decoder etc. The main applications of the decoder are data demultiplexing, digital display, digital to analog converters and memory addressing.