# 20 the nand gate is said to be an universal gate

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Unformatted text preview: on. That is, it is an electronic circuit that generates an output signal which is the reverse of the input signal. A NOT gate is also known as an inverter because it inverts the input. 16. A NAND gate is a complemented AND gate. That is, the output of NAND gate will be a 1 if any one of the inputs is a 0 and will be a 0 only when all the inputs are 1. 17. A NOR gate is a complemented OR gate. That is, the output of a NOR gate will be a 1 only when all inputs are 0 and it will be a 0 if any input represents a 1. 18. The logic gates are interconnected to form gating, or logic, networks which are known as combinational logic circuits. 19. The AND, OR, and NOT gates are logically complete in the sense that any Boolean function may be realizec using these three gates. 20. The NAND gate is said to be an universal gate because it is alone sufficient to implement any Booleai function. Similarly, the NOR gate is also an universal gate. 21. Exclusive-OR and equivalence, denoted by © and O respectively, are binary operations that perform the following Boolean functions: A©B=AB+AB 22. The design of combinational circuits starts from the verbal outline of the problem and ends in a logic circuit diagram. The procedure involves the following steps: (a) State the given problem completely and exactly. (b) Interpret the problem and determine the available input variables and required output variables. (c) Assign a letter symbol to each input and output variables. (d) Design the truth table that defines the required relations between inputs and outputs. (e) Obtain the simplified Boolean function for each output. (f) Draw the logic circuit diagram to implement the Boolean function. Questions 1. Explain the principle of duality in Boolean algebra. How is it useful? 2. Give the dual of the following Boolean expressions: (a) A + B (b)A + B + C (c) A •B + A-B (d) A + B (e) A • (A + B) (f) A + A • B 3. Give the dual of the rule A+A •B = A + B 4. Prepare truth tables for the following Boolean expressions: (a) AB + AB (e) ABC (b) ABC + BC (f) AB • C...
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## This document was uploaded on 04/07/2014.

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