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計算機概論 Homework#2 Ch. 3 3.1 In the following table, write whether each type of transistor will act as an open circuit or a closed circuit Ans: 3.2 Replace the missing parts in the circuit below with either a wire or no wire to give the output OUT a logical value of 0 when the input IN is a logical 1. Ans: 3.5 Complete a truth table for the transistor-level circuit in Figure 3.34. Figure 3.34 Diagram for Exercise 3.5 Ans: 3.6 For the transistor-level circuit in Figure 3.35, fill in the truth table. What is Z in terms of A and B? Figure 3.35 Diagram for Exercise 3.6 Ans: ; 3.7 The circuit below has a major flaw. Can you identify it? Hint: Evaluate the circuit for all sets of inputs. Ans: There is short circuit (path from Power to Ground) when either A = 1 and B = 0 or A = 0 and B = 1. 3.9 Fill in the truth table for the logical expression NOT(NOT(A) OR NOT(B)). What single logic gate has the same truth table? Ans: AND gate has the same truth table. 3.10 Fill in the truth table for a two-input NOR gate. Ans: 3.12 Following the example of Figure 3.11a, draw the gate-level schematic of a threeinput decoder. For each output of this decoder, write the input conditions under which that output will be 1. Ans: A B C A,B,C = 0 0 0 A,B,C = 0 0 1 A,B,C = 0 1 0 A,B,C = 0 1 1 A,B,C = 1 0 0 A,B,C = 1 0 1 A,B,C = 1 1 0 A,B,C = 1 1 1 3.16 Given the following truth table, generate the gate-level logic circuit, using the implementation algorithm referred to in Section 3.3.4. Ans: A B C Z 3.22 Implement a 4-to-1 mux using only 2-to-1 muxes making sure to properly connected all of the terminals. Remember that you will have 4 inputs, 2 control signals, and 1 output. Write out the truth table for this circuit. Ans: