Service manual

STP 11-25R13-SM-TG
Q - 20
b. AND function
. An AND gate performs the mathematical operation of conjunction as discussed
earlier. It requires that all inputs are present at the same time to get an output. The symbol for an AND
gate is shown in Figure Q-5 along with the Boolean algebraic expression, truth table, and waveforms.
Figure Q-5. AND Gate
(1) A typical IC that performs the AND function may have four gates in one IC or there may be only
one gate depending on the inputs. AND gates are not listed to two inputs. A typical IC containing AND
gates is shown in Figure Q-6.
Figure Q-6. 7408 Quad-Two Input AND Gate
(2) In a schematic where all the gates may not be located in the same place, there will be individual
gate symbols drawn with the IC number and pin numbers labeled as in Figure Q-7.
Figure Q-7. AND Gate
(3) Also, on the IC device itself, there is usually a notch on one end. While holding the notch to your
left and starting with the bottom left pin that is number 1, you can count the pin numbers in a
counterclockwise direction. Refer back to Figure Q-6.