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Electronic Labs_115

# Electronic Labs_115 - Fig 3-13 Truth tables for gates AND...

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Unformatted text preview: Fig. 3-13 Truth tables for gates. AND and NAND Boolean expression for the AND gate (A - B) and the NAND (A - B) is shown on the logic diagram in Fig. 34th). The truth table for the NAN D gate is shown at the right in Fig. 3-13. Notice that the truth table for the NAND gate is developed by in- verting the outputs of the AND gate. The AND gate outputs are also given in the table For reference. NAND gates are commonly employed in industrial practice and extensively used in all digital equipment. Do you know the logic symbol. Boolean expression. and truth table for the NAND gate? You must commit these to memory. 3-5 THE NOR GATE The NOR gate is actually a NOT OR gate. In other words. the output ofan OR gate is in- verted to-formaNOR ate. The logic symbolv for the NOR gate is diagramed in Fig. 3-l4ta). Note that the NOR symbol is an OR symbol with a small invert bubble tsrnall cir- cle} on the right side. The NOR function is being performed by an OR gate and an in- verter in Fig. 3—th1. The Boolean espres— A Y B (a) INPUTS A A +3 —— + B B A to} Fig. 3-14 to) NOR gate logic symbol. (b) A Boolean expression for the output of a NOR gate. Fig. 3-15 Truth table for OR and NOR gates. sion for the OR function (A + B) is shown. The ﬁnal NOR function is given the Boolean expression A + B. The truth table for the NOR gate is shown at the right in Fig. 3-13. Notice that the NOR gate truth table is just the complement of the output of the OR gate. The output of the OR gate is also included in the truth table in Fig. 3-13 for reference. You now should memorize the symbol, Boolean expression. and truth table for the NOR gate. You will encounter these items often in your work in digital electronics. 3-6 THE EXCLUSIVE OR GATE The exclusive OR gate is sometimes referred to as the “any but not all gate." The exclusive OR gate is often shortened to the XOR gate. The logic symbol for the XOR gate is dia- gramed in Fig. 3-l6(a); the Boolean expression for the XOR function is illustrated in Fig. 3-16(b). The symbol 63 means the terms are XORed together. A truth table for the XOR gate is shown at the right in Fig. 3-17. Notice that if any but A Y B (a) AjD—AoB B (b) Fig. 3-16 (at) XOR gate logic symbol. (b) A Boolean expression for the output of an XOR gate. INPUTS Binary Logic Gates CHAPTER 3 NOR gate Exclusive OR gate 15 ...
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