Embed Size (px)
Citation preview
CHAPTER 4 SECTION 1
ELECTRONIC SIGNALS & SEMICONDUCTORS
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
Electronics
the use of electronic current to control, communicate, and process information.
• Electronic Signal – varying electric current that represents information.
Analog Signals
• In an analog signal, a current is varied smoothly to represent information
Digital Signal
• In digital signals, pulses of current are used to represent information.
Semiconductors
A material that conducts current better than insulators but not as well as conductors.
A semiconductor conductscurrent much more easily.
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.
• 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.
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.
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.
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.
