When you order ICs, be careful to order an IC in a DIP package. If you obtain an
IC in a non-DIP package, such as an SOIC (see the earlier section, “Transistors”),
you can try forever, but you will never be able to insert the leads into a board.
High-volume manufacturers use these other ICs with a technique called sur-
face mounting.In this technique, the leads are soldered onto a contact on the
surface of a circuit board, not inserted into a hole. If you really need to use an
IC that comes only in a surface mount-type package, look for adapters to which
you can solder the surface-mount IC and then insert the adapter into your
board.Because ICs are simply a collection of components (such as transistors, resis-
tors, and capacitors) stuffed in miniature onto a silicon chip, each type of IC
can perform a different function. That function depends on how many of each
component is placed on the chip and how they are wired together. The next
two sections provide an overview of two common ICs: operational amplifiers
and audio amplifiers.Opting for op amps
Operational amplifiers (affectionately known as op amps) are a type of IC that
contains a series of transistors; each transistor amplifies the voltage of the
signal just a bit more. You could build a multistage transistor amplifier that
could do a similar job by using several transistors, capacitors, and resistors,
but why bother? This setup would use about 50 times more space on your
breadboard than a single 8-pin DIP op amp.If you look in a catalog for op amps, you’ll probably see pages and pages of
them — they’re that popular. The fact that we’re using 6 volt batteries to power
our circuits narrows down the list considerably. Many op amps are designed to
work with a positive supply voltage and a negative supply voltage, such as +6
volts and –6 volts. We use op amps in our projects that are designed to work
with a 6 volt, or less, single-sided supply. An op amp that is designed to work
with a single-sided supply needs only a positive supply voltage and ground.Op amp ICs usually come in 8-pin DIPs; some of these have one op amp cir-
cuit, and some have two op amps (dual op amps).In a dual op amp, the pins
that give access to one op amp are on the left side of the DIP, and the pins
that give access to the other op amp are on the right side of the DIP. As you
can see in the project in Chapter 7, this allows you to build one portion of
your project circuit along the left side of the breadboard and a second por-
tion along the right side of the breadboard, which can come in handy if things
get overcrowded. Op amp ICs also come in 14-pin DIPs. These contain four
separate op amps and are therefore called quad op amps.Here are some common op amps used in electronics projects using low-volt-
age batteries:LM358:A dual op amp
LM324:A quad op amp44 Part I: Project Prep