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Circuit Description

This applet shows a BCD to seven segment decoder implemented as a two-level AND-OR circuit. It converts a 4-bit binary-coded decimal value, that is the numbers 0 to 9 coded as 0000 to 1001, into the code required to drive a seven-segment display.

Note that several realization variants are possible, depending on the terms chosen during logic minimization and the decision on how to handle the inputs values above 9. This circuit follows the example presented and explained in Schiffmann, Schmitz, Technische Informatik I, 4.15, p.170.

Another popular choice is to display the letters A,b,C,d,E,F for the corresponding input values 10 to 15. Yet another scheme is used by the TTL-series 7447..7449 circuits, which generate (apparently) meaningless output signals for these input values.