a) Combinational logic circuits are circuits where the outputs are determined by the present combination of inputs only, while sequential logic circuits are circuits where the outputs are determined by both present and past inputs. The design requirements of combinational circuits are specified by the number of logic gates they contain, which classifies them according to the circuit complexity. b) Schottky transistors have low switching time, hence low propagation delay. c) Function implemented as shown below: A B C 3-to-8 Decoder 1 2 3 4 5 6 7 S(A,B,C) = m(1,2,4,7) C(A,B,C) = m (3,5,6,7) d) a. 4-to-1 Multiplexer with ENABLE input. DESIGN: Io 1 13 4-to-1 Multiplexer with ENABLE input S E This multiplexer accepts four data points and allows only one of them to get to the output. The data selection is determined by the SELECT input code, which is given bySSo. The ENABLE input controls the operation of the multiplexer. The output of the multiplexer is LOW when the ENABLE is LOW. lo 4 1 13 S SE E 0 LOGIC DIAGRAM: TRUTH TABLE: INPUTS S X So X OUTPUT Z 0 Z 1 1 1 1 . 0 0 1 1 0 1 0 1 Io 1 13 EXPRESSION FOR Z: Z=10 (55) +4-(5S)+ 1 (S50) + 1 (S, S.) b. Decoder as a de-multiplexer Using a 2-line-to-4-line decoder with ENABLE input as an example of a de-multiplexer, The ENABLE input of the decoder is used as the data input in the de-multiplexer, since the de-multiplexer takes one data input and distributes it to 1 of N output channels. Y Y Yo The data inputs of the decoder,A, A, are used as the SELECT inputs of the de-multiplexer.