Integrated Circuit chips

Figure below shows what is often referred to as an integrated circuit (IC). The circuit is actually etched onto a tiny wafer or “chip” of silicon, embedded in a black plastic body, which is properly referred to as the “package.” Tiny wires inside the package link the circuit with the two rows of pins on either side.

                                    

 

   

                                                                                                                                                                                                                                                                                 

          

Figure 4-2. An integrated circuit chip in Plastic Dual-Inline Pin package, abbreviated PDIP, or, more often, DIP.The pins are mounted at intervals of 1/10 inch in two rows spaced 3/10 inch apart. This format is known as a Plastic Dual Inline Package, abbreviated PDIP, or, more often, just DIP. The chip in the photograph has four pins in each row; others may have many more. The first thing you need to know, when shopping for chips, is that you’ll only be using the DIP package. Figure 4-3 shows a size comparison between a 14-pin DIP package and a 14-pin surface-mount package. Many surface-mount chips are even smaller than the one shown.Just about every chip has a part number printed on it. In Figure 4-2, the part number is KA555. In Figure 4-3, the DIP chip’s part number is M74HC00B1, and the surface-mount chip is a 74LVC07AD. You can ignore the second line of numbers and/or letters on each chip, as they are not part of the part number.

Notice in Figure 4-3 that even though the chips look quite different from each other, they both have “74” in their part numbers. This is because both of them are members of the “7400” family of logic chips, which originally had part numbers from 7400 and upward (7400, 7401, 7402, 7403, and so on). Often they are now referred to as “74xx” chips, where “xx” includes all the members of the family.  The DIP chip, at the rear, has pins spaced 1/10 inch apart, suitable for insertion in a breadboard or perforated board. It can be soldered without special tools. The small-outline integrated circuit (SOIC) surface-mount chip 

(foreground) has solder tabs spaced at 1/20 inch. Other surface-mount chips have pins spaced at 1/40 inch or even less (these dimensions are often expressed in millimeters).

 Surface-mount chips are designed primarily for automated assembly and are difficult to work with manually. In this photo, the yellow lines are 1 inch apart to give you an idea of the scale.Take a look at Figure 4-4, which shows how to interpret a typical part number in a 74xx family member. The initial letters identify the manufacturer (which you can ignore, as it really makes no difference for our purposes).
Skip the letters until you get to the “74.” After that, you find two more letters, which are important. The 74xx family has evolved through many generations, and the letter(s) inserted after the “74” tell you which generation you’re dealing with. Some generations have included:

•  74L
•  74LS
•  74C
•  74HC
•  74AHC
And there are more.