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 Electronics Paper 2, May/June 2008
 Questions: 1 2 3 4 5, 6 & 7 8 9 10 Main
Weakness/Remedies
Strength
Question 9

Figure 8
(a) Draw the truth table for the logic circuit in figure 8.
(b) State the output Boolean expression in figure 8.
(c) State the input condition at which the output is logic 1.

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OBSERVATION

The expected answers were:
(a)          The truth table for the logic circuit as is as shown below.

 A B C F 0 0 1 0 0 1 1 1 1 0 1 0 1 1 0 0

(b)          The Boolean expression that relates the output to the input is
F = (A.B) . B = C.B
(c)           As can be seen from the truth table, F is at the logic level 1 only when A = 0 and B = 1. The                            equation was on digital electronics. The question was popular with the candidates. Quite a                        few candidates gave more than four correct responses.