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Semiconductors Chapters
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Tubes
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Semiconductors
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Silicon Atom
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Germanium Atom (Less abundant than Silicon!!)
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Intrinsic Material Pure Substance No Impurities!
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Negative Temperature Coefficient
Silicon Low Temperature – Poor Conductor High Temperature – Good Conductor Negative Temperature Coefficient Temperature Increases – Resistance Decreases
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Covalent Bond Share 2e- Silicon Si Si Si Si Si Si Si Si Si Si Si Si
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Doped Material – N-Type (electrons – majority carrier)
As Si Si Si e- Si As Si Si e- Si Si As Si
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Doped Material – P-Type (holes – majority carrier)
Si Si Ga Si + Si Si Si Ga HOLE + Si Si Ga Si HOLE +
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N - Material e- e- e- e- e- e- e- e- e- e- e-
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P Material + + e- + + + e- + + + e- e- e- e-
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N Type: Negative Charge (-)
P – N Type Material N Type: Negative Charge (-) P Type: Positive Charge (+)
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Advantages of Semiconductors
Smaller Low Power Cheaper High Efficiency Great Reliability Runs Cooler More Rugged Long Life Hazardous Environment Economic Production Less Noisy Made Part of an I.C. (Integrated Circuit)
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Disadvantages of Semiconductors
Susceptible to Temperature Changes. Extra components for Stabilization. Easily Damaged Exceeding Power Limits Reversing Polarity Excess Heat when Soldering
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The PN Junction
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An area that has no majority carriers.
P-N Junction P N e- + { Depletion Region An area that has no majority carriers.
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P N { + e- e- + + e- + e- e- + e- + + e- P-N Junction Barrier Voltage
Build up of charge for each side. Must be overcome to conduct.
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- + e- + e- e- + + e- + e- e- e- + e- + Diode Operation
Bias Voltage Reversed Bias (No Current Flow) There is a small Leakage Current that can flow!!!
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- + + e- + e- + e- e- e- e- e- + e- + e- + e- + e- + e- + e- +
Diode Operation + e- + e- + e- e- e- e- e- + e- - + e- + + e- + e- + e- + e- + Once the barrier voltage is exceeded!! Forward Bias (Current Flows)
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Forward Biased Diode EF is the Forward Voltage on the Diode
EF for Germanium is 0.3V EF for Silicon is 0.7V
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Example: What is the Forward Biased Current (IF)? Germanium Diode
+ EF= 0.3V R = 10kΩ Es= 9V IF= ER R ES - EF R = 9V - 0.3V 10kΩ = 0.87mA =
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Diode Operation – Forward Biased
+ - +
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Current e- + - +
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Manufacturers Specifications
Maximum Forward Current Maximum Reverse Voltage
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One Directions!!!
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Diode Symbol P N Anode Cathode
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Diode Current Flow Anode Cathode
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Diode Identification White or Silver Line on Anode Anode Cathode
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Diode Construction Grown Junction Alloyed Junction Diffused Junction (Most Common)
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Diode Testing Low Resistance High Resistance
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LED – Light Emitting Diodes
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LED – Light Emitting Diodes
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LED – Light Emitting Diodes
Electron High Energy + Hole Low Energy
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LED – Light Emitting Diodes
Electron and Hole Combine +
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Zener Diode Made to operate at a voltage greater than normal breakdown voltage. Manufacture with a specific voltage in mind. Voltage is determined by the resistance.
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Zener Diode Symbol
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Temperature Coefficient
Positive – Breakdown voltage increases with Temperature. Operate in the 4 – 5 volt range Negative – Breakdown voltage Decreases with Temperature. Operate at less than 4 volts.
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Silicon Controlled Rectifier (SCR)
Anode Cathode Gate
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Silicon Controlled Rectifier (SCR)
Turn on Gate Diode Works!!!!
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Transistor
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Bipolar or Junction Transistor. Three layer device. Amplification
Switch
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N-P-N Transistor Collector N Base P N Emitter
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P-N-P Transistor Collector P Base N P Emitter
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Transistor Use Type Material Major Use NPN PNP Germanium Silicon
High or Low power Switching High Frequency
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Transistor Packaging
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Transistor Packaging Part Number
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Transistor Operation
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Collector Base Emitter
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IC IB IE e- e- e- e- e- e- e- e- + + + + e- e- e- e- e- e- C B E
N-P-N Transistor IC C e- e- e- e- e- IB e- e- e- B + + + + e- e- Diode Turns On!!! e- e- e- e- IE E
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IC IB IE + + + + + + + + + + C B E P-N-P Transistor Diode Turns On!!!
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Transistor Testing - Resistance
Forward – Low Resistance C B E Reverse – Low High Resistance
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Transistor Testing
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