CCTC: Industrial Technology Electrical Systems

1. CCTC: Industrial Technology Electrical Systems

2. Conductors Conductors– are elements that easily give up electrons. This means they offer little resistance to current flow, thus electrical current flows freely through them without a lot of energy applied. They also conduct heat. • Normally a conductor has 3 or less electrons in their last valence shell • Good conductors are Malleable (can be easily bent, shaped, and rolled without cracking) and Ductile (can be drawn out into a thin wire strand.) Copper Atom has only 1 electron in its outer Valence Shell Copper, Silver, and Gold are excellent conductors of electricity

3. Conductors Aluminum is used in commercial wiring but it is not the best conductor

4. Insulators Insulators– are elements that do not easily give up electrons. This means they prevent current flow, thus electrical current does not flow freely through them. • Insulators have 5 or more electrons in their outer Valence Shell • Compounds such as glass, porcelain, air, wood, paper, rubber and plastic are excellent insulators.

5. Semiconductors • Semiconductors– are elements that aren’t really good conductors, but cannot be used as insulators either. They can conduct electricity but cannot conduct heat. Sometimes their called false metals or metalloids • Semiconductors have 4 electrons in their outer Valence Shell • Germanium and Silicon are important elements that are used as semiconductors. Germanium Atom has 4 electrons in its outer Valence Shell

6. Silicon • Silicon usually doesn’t exist as a separate element in nature but is abundant in rocks and minerals. • Silica is a compound of Silicon and Oxygen. Sand, granite, quartz, and Opai are all forms of Silica. It’s the second most abundant compound in the Earth. • Silicon is very important in the “High Tech” industry since it is used to control the electric current in computers and other digital hardware. • Silicon Valley is the area in California that manufactures many of these control circuits or semiconductors. Silicon Atom has 4 electrons in its outer Valence Shell

7. DOPING MATERIALS DOPINGis the process of adding impurities to pure semiconductive in order to make them conduct electricity better. Impurities can be either considered donors or acceptors • Donors easily give up electrons and semiconductors doped with donors are called N-Type (Negative) material. • Acceptors produce a “hole” (an absence of an electron) and semiconductors doped with acceptors are called P-Type (Positive) material. When voltage is applied, the holes become carriers for free flowing electrons.

8. PN JUNCTIONS When P-Type Material is joined with N-Type Material, a PN Junction is formed. An interesting phenomenon occurs that allows current to flow through it in only one direction. The P-Type Material is called the Anode and the N-Type Material is called the Cathode. This phenomenon is the foundation of Solid State Electronics.

9. Depletion Region • At the PN Junction the electrons (-) are naturally attracted to the holes (+), thus they join together through a process called diffusion. This area is called the Depletion Region.

10. BIAS • The term BIAS means simply applying voltages to a semiconductor in order to make it function. Remember, voltage is the Difference of Potential (FORCE) that makes current flow. • Semiconductors function basically like a switch. Either it’s on and current flows through it, or it’s off and current does not flow through it. • FORWARD BIAS is applying voltages so the semiconductor allows current to flow (switch turns on). • REVERSE BIAS is applying voltages so the semiconductor does not allow current to flow (switch is off).

11. FORWARD BIASED • In a Forward Biased semiconductor, we apply negative voltage on the negative side and positive voltage on the positive side. • The electrons are repelled by the negative voltage on the negative side and attracted to the positive voltage on the positive side. • Likewise the holes are repelled by the positive voltage on the positive side and attracted to the negative voltage on the negative side. • There must be at least a 0.7 volt difference of potential in order for the electrons to cross the depletion region. • The Depletion Region is small and current flows from negative to positive

12. REVERSED BIASED • In a Reversed Biased semiconductor, we apply positive voltage on the negative side and negative voltage on the positive side. • The electrons are attracted to the positive voltage on the negative side and repelled from the negative voltage on the positive side. • Likewise the holes are attracted to the negative voltage on the positive side and rebelled from the positive voltage on the negative side. • There must be at least a 0.7 volt difference of potential in order for the electrons to cross the depletion region. • The Depletion Region is much bigger and current WILL NOT flow through a reversed biased semiconductor.

13. Examples of Bias FORWARD BIASED • Negative voltage on N-Type Material and Positive voltage on P-Type Material. • current flows from negative to positive • REVERSED BIASED • Positive voltage on N-Type Material and Negative voltage on P-Type Material. • current does not flow

14. DIODE • Diodes are the simplest type of semiconductor. The arrow always points to the N-Type Material and current flows from negative to positive against the arrow when it is FORWARD BIASED.

15. Diode Operating Characteristics As forward bias is increased, current will not flow until the voltage overcomes the 0.7 vdc barrier voltage created by the depletion region. Once voltage is greater than 0.7 vdc, current flows. When the Diode is reverse biased, current will not flow. However, if the reverse bias voltage is great enough, the Diode will “break down” and current will flow so heavily, that it’s called an Avalanche. In most cases, an avalanche will destroy the Diode.

16. Rectification Rectification is a “process” of converting Alternating Current into Direct Current and it begins with a diode. Another name for a Diode is a Rectifier Diodes are basically electronic switches that only conduct one way

17. Regulation Voltage Regulation is the process of maintaining a constant, unchanging voltage output regardless of the voltage input. ZENER Diodes are Special Purpose diodes designed to operate in the “Reverse Bias Breakdown” region. Current Avalanche is the desired outcome for a Zener Diode.

18. Light Emitting Diode (LED) LED’s (Light Emitting Diodes) are special purpose diodes that are designed to emit light when current flows through them. When forward biased, electrons are able to recombine with holes and release energy in the form of a photon (light). LED’s are used as indicator lamps, automotive lamps, flashlights, traffic symbols.

19. Various Semiconductors