Service manual

STP 11-25R13-SM-TG

Q - 23

(4) The second way of constructing a NAND gate is to feed the inputs into an AND gate and then

invert the output. This method and truth table are shown in Figure Q-13.

Figure Q-13. NAND Gate (alternate)

_ _ __

(5) Therefore, as shown in Figures Q-12 and Q-13, A + B = AA. A typical NAND IC would have the

symbol shown in Figure Q-14.

Figure Q-14. NAND Gate Symbol

f. NOR Function

. NOR is another type of gate that can be constructed from the three basic gates

(AND, OR, and NOT).

(1) A NOR gate is the complement of the OR gate. Again, you can look at the truth table for an OR

gate and develop a truth table for the NOR gate by inverting the outputs of the OR gate. See Table Q-14.

Table Q-14. Truth Tables

(2) Just as in the case of the NAND gate, there are also two ways to construct a NOR gate. The

first is to feed the inputs into an AND gate after they have been inverted. Figure Q-15 shows this along

with the truth table.

Figure Q-15. NOR Gate

OR Table NOR Table

A B C

0 0 0 0 0 1

0 1 1 0 1 0

1 0 1 1 0 0

1 1 1 1 1 0