2-16Q18.What is the output Boolean expression for a NAND gate with inputs A, B , and C?Q19.A NAND gate has inputs labeled as A, B , and C. If A and B are HIGH, C must be at what logiclevel to produce a HIGH output?THE NOR GATEAs you might expect, the NOR gate is an OR gate with an inverter on the output.LOGIC SYMBOLThe standard logic symbol for this gate is shown in figure 2-14. More than just the two inputs maybe shown.Figure 2-14. —NOR gate.The NOR gate will have a HIGH output only when all the inputs are LOW.When broken down, the two functions performed by the NOR gate can be represented by theequivalent circuit depicted in figure 2-15. When both inputs to the OR gate are LOW, the output is LOW.A LOW applied to an inverter gives a HIGH output. If either or both of the inputs to the OR gate areHIGH, the output will be HIGH. When this HIGH output is applied to the inverter, the resulting output isLOW. The Boolean expression for the output of this NOR gate is f = K L+. The expression is spoken,"K OR L quantity NOT."Figure 2-15. —NOR gate equivalent circuit.NOR GATE OPERATIONThe logic level inputs and corresponding outputs for a NOR gate are shown in figure 2-16. At timeT0, both K and L are LOW; as a result, f is HIGH. At T1, K goes HIGH, L remains LOW, and f goesLOW. At T2, K goes LOW, L goes HIGH, and the output remains LOW. The output goes HIGH again atT3 when both inputs are LOW. At T4 when both inputs are HIGH, the output goes LOW and remainsLOW until T5 when both inputs go LOW. Remember the output is just opposite of what it would be for anOR gate.
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business
