152 Engineering Fundamentals
Integrated Circuits (ICs)
An integrated circuit (IC) consists of multi-
ple electronic circuits etched into a thin layer of
silicon and enclosed in a protective material like
plastic. A dot or notch on the outside of the chip is
used for orientation. ICs contain resistors, capaci-
tors, diodes, transistors, and the conductors to
connect the circuits. Some ICs are very sensitive
to static electricity, or charge buildup. It is impor-
tant to take antistatic precautions when working
with these ICs. See Figure 8-22.
One of the most common ICs is the 555 timer. It
includes 23 transistors, two diodes, and 16 resistors.
The 555 timer has literally thousands of applications.
The 555 can be connected in a circuit in one of two
ways: monostable or astable. When used in mono-
stable mode, it creates an output for a given period
of time. Think of a seatbelt indicator on a dashboard
of a car that turns on to tell the driver to use the
seat belt, but turns off after a given period of time.
555 timers can also be used in astable mode, where
a repetitive pulse is created. An example of this
could be the repetitive buzzing of an alarm clock.
Figure 8-23 shows the 555 timer and its pin diagram.
Power Supply
Capacitor
A
SPST Switch
When the switch is closed, the ammeter will read some
current flow until the capacitor reaches saturation.
Figure 8-21.
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Antistatic wrist strap
It is important to take antistatic precautions when working
with ICs because they are very sensitive to charge buildup.
One type of precaution is this antistatic wrist strap.
Figure 8-22.
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1. Ground
2. Trigger
3. Output
4. Reset
8. Vcc
7. Discharge
6. Threshold
5. Control voltage
555
Figure 8-23.
This diagram shows
a 555 timer and pin
configuration.