Digital Design_ Principles and Practices, Chegg Solution Manual_parte_147

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Step of 7 4.040E Consider the following 2-input AND gate which have one input in inverted form: A Z B Figure 1 Step 2 of 7 In Figure 1, A and B are inputs to the gate whereas Z is the output. The gate in Figure 1 can also represented as shown in Figure 2. A Z B Figure 2 Step of 7 This type of gate represented in Figure 2 is called inhibit gate or anti-coincidence circuit or enable/disable circuit. Because, one input acts as a controller for the circuit that is, according to the input B the gate enables or disables. If the gate conducts and the output varies according to the input A else if then the gate does not conduct and it gives the result 0, whatever will be the A value. Thus this is called as inhibitor circuit or enable/disable circuit. Multiple input inhibitor circuit also possible and in a single gate it is possible to have more than one inhibited terminal. The standard AND gate does not be an inhibitor circuit and it is called as uninhibited. The 2-input AND gate with one input inverted or inhibited does not form a complete set because using this inhibited gate it is not possible to implement AND, OR and NOT gates. Because if the inhibit gate is connected in any order, the result will be same as shown in the Figure 1 or value 0. The output of 2-input AND inhibit gate gives the result as Step of 7 Try to connect two inhibited gates as shown in Figure 3. A B Z B Figure 3 Step of 7 Find the output of circuit in Figure 3. since since x Thus, the output of the gate in Figure 3 is same as the output of the gate in Figure 1. Step of 7 Try to connect three inhibited gates as shown in Figure 4. A B A B Figure 4 Step of 7 Find the output of circuit in Figure 4. since =0 since 0 Thus, observe that the result of the inhibit gate connected in any manner is same as the result of gate in Figure or value 0. Hence, the 2-input AND gate with one input inverted or inhibited gate does not form a complete set.