BCD to 7 segment decoder

In BCD (Binary Coded Decimal), a binary pattern is used to represent a decimal number. A 7 segment display is used to display hexadecimal numeral by seven LEDs arranged in a definite pattern as shown in figure (a).

bbcd to 7 segment decoder

A BCD to 7 segment decoder accepts the BCD code on its input and provide output to drive a 7 segment display.

For example, if the BCD code in the input is 0011 then we have to display decimal 3 on the 7 segment display. From the figure(b) it is clear that to display a 3 on a seven-segment display we have to enable LEDs a,b,c,d and g. So the output lines should be a=,b=1,g=1,c=1 and d=1.

7 seg display 1

The truth table for a seven segment decoder is given below,

Decimal DigitInputDecoding functionOutput
A0A1A2A3abcdef g
00000{abcdef \overline g}1111110
10001{\overline a bc \overline d \overline e \overline f \overline g}0110000
20010{ab \overline c de \overline f g}1101101
30011{abcd \overline e \overline f g}1111001
40100{\overline a bc \overline d \overline e f g}0110011
50101{a \overline bcde \overline f g}1011011
60110{a \overline b cdefg}1011111
70111{abc \overline d \overline e \overline f \overline g}1110000
81000{abcdefg}1111111
91001{abcd \overline e fg}1111011

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