6thgrade ch.4sec.1electronicsignals

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.

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

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.