This document provides an overview of electronic signals, semiconductors, and some basic electronic components. It discusses how Morse code was used for early radio communication before voice transmission. It defines analog and digital signals and introduces semiconductors as materials that conduct electricity better than insulators but not as well as conductors. Key components like diodes, transistors, and integrated circuits are summarized, including their basic functions and compositions.

1. CHAPTER 4 SECTION 1
ELECTRONIC SIGNALS
& SEMICONDUCTORS

2. Morse Code
• Developed by Samuel Morse in 1836
• In the 1890s, before it was possible to
transmit voice, Morse code began to be used
for early radio communication.
• Original intent was just to send numerals,
Alfred Vail expanded it to include letters and
special characters

4. Electronics
the use of electronic current to control,
communicate, and process information.
• Electronic Signal – varying electric current that
represents information.

5. Analog Signals
• In an analog signal, a current is varied
smoothly to represent information

6. Digital Signal
• In digital signals, pulses of current are used to
represent information.

7. http://www.youtube.com/watch?v=8Ei8D08V4-4

8. Semiconductors
A material that conducts current better than
insulators but not as well as conductors.
A semiconductor conducts
current much more
easily.

9. How can a material conduct current
only under certain conditions?
• Silicon and other semiconductors are
elements that have extremely high
resistance
• By adding atoms of other elements to
semiconductors, the resulting material
can conduct current much more easily.

10. • Adding atoms with extra electrons to silicon
produces an n-type semiconductor. “N” indicates
that the material can release, or give off, electrons.
• Adding atoms with fewer electrons, or holes, to
silicon produces a p-type semiconductor. “P”
indicates that the material has room for and can
receive an electron.

11. Diodes
• An electronic component that consists of an n-
type and a p-type semiconductor joined
together.
• A diode allows current in one direction only.
• Diodes can be used to change an alternating
current to a direct current or as a switch.

12. Transistors
• When a layer of one type of semiconductor is
sandwiched between two layers of the other
type of semiconductor, a transistor is formed.
• A transistor has two uses: it either amplifies
an electronic signal or switches current on and
off.

13. Integrated Circuits
• A combination of individual electronic
components into larger groups.
• An integrated circuit is a thin slice of
semiconductor that contains many diodes,
transistors, and other
electronic components.
• Integrated circuits are
also called chips.