SEMICONDUCTORSSEMICONDUCTORS

Sir Gian’s Sir Gian’s Physics Physics

Since Since 2001220012

IntroductionIntroduction Semiconductors are materials Semiconductors are materials

whose electrical properties lie whose electrical properties lie between Conductors and between Conductors and Insulators.Insulators.

Ex : Silicon, Germanium, Aluminum…Ex : Silicon, Germanium, Aluminum…

What are P-type and N-What are P-type and N-type ?type ?

Semiconductors are DOPED (giving of extra Semiconductors are DOPED (giving of extra elements) in to P-type and N-type elements) in to P-type and N-type semiconductorsemiconductor

P-type: A P-type material is one in which P-type: A P-type material is one in which holes are majority carriers i.e. they are holes are majority carriers i.e. they are positively charged materials (++++) USES positively charged materials (++++) USES GROUP III ELEMENTS (Al, Ga, In,)GROUP III ELEMENTS (Al, Ga, In,)

N-type: A N-type material is one in which N-type: A N-type material is one in which electrons are majority charge carriers i.e. electrons are majority charge carriers i.e. they are negatively charged materials (-----) they are negatively charged materials (-----) USES GROUP V ELEMENTS (P, As, N, Sb)USES GROUP V ELEMENTS (P, As, N, Sb)

Extra Extra electrons are electrons are the KEY to the KEY to their their operationoperation

Vacancy of Vacancy of electrons is electrons is the key to the key to their their operationsoperations

DiodesDiodes

Electronic devices created by Electronic devices created by bringing together a bringing together a pp-type and -type and nn--type region within the same type region within the same semiconductor lattice. Used for semiconductor lattice. Used for rectifiers, LED etcrectifiers, LED etc

DiodesDiodes

It is represented by the following It is represented by the following symbol, where the arrow indicates symbol, where the arrow indicates the direction of positive current the direction of positive current flow.flow.

Forward Bias and Forward Bias and Reverse BiasReverse Bias

Forward Bias : Connect positive of Forward Bias : Connect positive of the Diode to positive of supply…the Diode to positive of supply…negative of Diode to negative of negative of Diode to negative of supplysupply

Reverse Bias: Connect positive of Reverse Bias: Connect positive of the Diode to negative of supply…the Diode to negative of supply…negative of diode to positive of negative of diode to positive of supply.supply.

Characteristics of Characteristics of DiodeDiode Diode always conducts in one Diode always conducts in one

direction.direction. Diodes always conduct current when Diodes always conduct current when

“Forward Biased” ( Zero resistance)“Forward Biased” ( Zero resistance) Diodes do not conduct when Reverse Diodes do not conduct when Reverse

BiasedBiased

(Infinite resistance)(Infinite resistance)

Quiz Quiz 1.1. It is the act of adding extra elements to a It is the act of adding extra elements to a

semiconductor.semiconductor.

2.2. It is the bias of a diode that allows It is the bias of a diode that allows current flow.current flow.

3.3. Group in the periodic table that is added Group in the periodic table that is added to a semiconductor, making it an N-typeto a semiconductor, making it an N-type

4.4. Give an example of an element mainly Give an example of an element mainly used to make semiconductors.used to make semiconductors.

5.5. Diodes always conduct in ______ directionDiodes always conduct in ______ direction

Transistors Transistors

Made of 3 alternating Made of 3 alternating Semiconductors joint togetherSemiconductors joint together

Capable of transmitting signal and Capable of transmitting signal and amplificationamplification

Bipolar Junction Bipolar Junction Transistors (BJT)Transistors (BJT)

Have a pair of the same Have a pair of the same semiconductor, N or P. most semiconductor, N or P. most commonly used in the field of commonly used in the field of eletronics.eletronics.

npn BJT Transistorsnpn BJT Transistors

High potential at High potential at collectorcollector

Low potential at emitterLow potential at emitter Allows current flow Allows current flow

when the base is given when the base is given a high potentiala high potential

Acts as a switch, Acts as a switch, turning on the circuit, turning on the circuit, and and AMPLIFIER.and and AMPLIFIER.

pnp BJT Transistorspnp BJT Transistors

High potential at emitterHigh potential at emitter Low potential at collectorLow potential at collector Allows current flow when Allows current flow when

base is connected to a low base is connected to a low potentialpotential

Acts as a switch, blocking Acts as a switch, blocking the current. Also controls the current. Also controls the current flow, making the current flow, making it a regulator/valveit a regulator/valve

Operations of transistorsOperations of transistors

Saturation (Transistor acts as On Saturation (Transistor acts as On switch)switch)

Cutoff (Cutoff (Transistor acts like an off switch)Transistor acts like an off switch)

Active(Active(Transistor acts like a current amplifier)Transistor acts like a current amplifier)

Reverse (current flows in reverse )Reverse (current flows in reverse )

Saturation Saturation

Cut offCut off

ActiveActive

Quiz :DQuiz :D

1.1. Type of transistor that acts as a Type of transistor that acts as a switchswitch

2.2. Mode of transistors that amplify Mode of transistors that amplify signalssignals

3.3. Symbol of a PNP transistorSymbol of a PNP transistor

4.4. Transistors that have a pair of the Transistors that have a pair of the same semiconductorsame semiconductor

5.5. Mode of transistors that reverse the Mode of transistors that reverse the current flowcurrent flow