Semiconductors Chapters 19 20 22

Tubes

Semiconductors

Silicon Atom

Germanium Atom (Less abundant than Silicon!!)

Intrinsic Material Pure Substance No Impurities!

Negative Temperature Coefficient Silicon Low Temperature – Poor Conductor High Temperature – Good Conductor Negative Temperature Coefficient Temperature Increases – Resistance Decreases

Covalent Bond Share 2e- Silicon Si Si Si Si Si Si Si Si Si Si Si Si

Doped Material – N-Type (electrons – majority carrier) As Si Si Si e- Si As Si Si e- Si Si As Si

Doped Material – P-Type (holes – majority carrier) Si Si Ga Si + Si Si Si Ga HOLE + Si Si Ga Si HOLE +

N - Material e- e- e- e- e- e- e- e- e- e- e-

P Material + + e- + + + e- + + + e- e- e- e-

N Type: Negative Charge (-) P – N Type Material N Type: Negative Charge (-) P Type: Positive Charge (+)

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)

Disadvantages of Semiconductors Susceptible to Temperature Changes. Extra components for Stabilization. Easily Damaged Exceeding Power Limits Reversing Polarity Excess Heat when Soldering

The PN Junction

An area that has no majority carriers. P-N Junction P N e- + { Depletion Region An area that has no majority carriers.

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.

- + 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!!!

- + + 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)

Forward Biased Diode EF is the Forward Voltage on the Diode EF for Germanium is 0.3V EF for Silicon is 0.7V

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 =

Diode Operation – Forward Biased + - +

Current e- + - +

Manufacturers Specifications Maximum Forward Current Maximum Reverse Voltage

One Directions!!!

Diode Symbol P N Anode Cathode

Diode Current Flow Anode Cathode

Diode Identification White or Silver Line on Anode Anode Cathode

Diode Construction Grown Junction Alloyed Junction Diffused Junction (Most Common)

Diode Testing Low Resistance High Resistance

LED – Light Emitting Diodes

LED – Light Emitting Diodes

LED – Light Emitting Diodes Electron High Energy + Hole Low Energy

LED – Light Emitting Diodes Electron and Hole Combine +

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.

Zener Diode Symbol

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.

Silicon Controlled Rectifier (SCR) Anode Cathode Gate

Silicon Controlled Rectifier (SCR) Turn on Gate Diode Works!!!!

Transistor

Bipolar or Junction Transistor. Three layer device. Amplification Switch

N-P-N Transistor Collector N Base P N Emitter

P-N-P Transistor Collector P Base N P Emitter

Transistor Use Type Material Major Use NPN PNP Germanium Silicon High or Low power Switching High Frequency

Transistor Packaging

Transistor Packaging Part Number

Transistor Operation

Collector Base Emitter

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

IC IB IE + + + + + + + + + + C B E P-N-P Transistor Diode Turns On!!!

Transistor Testing - Resistance Forward – Low Resistance C B E Reverse – Low High Resistance

Transistor Testing