Semiconductors, such as Silicon (Si) are made up of individual atoms bonded together in a regular, periodic structure to form an arrangement whereby each atom is surrounded by 8 electrons.

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Presentatio

2. Semiconductor

3. Semiconductor :
Semiconductors, such as Silicon (Si) are made up of individual atoms
bonded together in a regular, periodic structure to form an arrangement
whereby each atom is surrounded by 8 electrons.
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4. Types of Semiconductors :
Semiconductors can be classified as:
1. Intrinsic Semiconductor.
2. Extrinsic Semiconductor.
Extrinsic Semiconductors are further classified as:
a. n-type Semiconductors.
b. p-type Semiconductors.
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5. Intrinsic Semiconductor:
Semiconductor in pure form is
known as Intrinsic
Semiconductor.
Ex. Pure Germanium, Pure
Silicon.
At room temp. no of electrons
equal to no. of holes.
Si
SiSi
Si
Si
Si
Si
Si
Si
FREE ELECTRON
HOLE
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6. N-type Semiconductor:
Arsenic atom has 5 valence electrons.
Fifth electron is superfluous, becomes free electron and enters
into conduction band.
Therefore pentavalent impurity donates one electron and
becomes positive donor ion. Pentavalent impurity known as
donor.
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7. P-type Semiconductor:
Gallium atom has 3 valence electrons.
It makes covalent bonds with adjacent three electrons of silicon
atom.
There is a deficiency of one covalent bond and creates a hole.
Therefore trivalent impurity accepts one electron and becomes
negative acceptor ion. Trivalent impurity known as acceptor.
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8. P – N Junction:
One of the crucial keys to solid state electronics is the nature of the P-N
junction. When p-type and n-type materials are placed in contact with each
other, the junction behaves very differently than either type of material
alone.
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9. Transistor:
A transistor is a device that regulates current or voltage flow and acts as a
switch or gate for electronic signals. Transistors consist of three layers of
a semiconductor material, each capable of carrying a current.
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10. Types of Transistor:
 common base connection
 common emitter connection
 common collector connection
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11. Forward Resistance:
1. Dynamic resistance (rf)= ΔV/ ΔI ..ohms.
Where ΔV, ΔI are incremental voltage and current values on
Forward characteristics.
2. Static resistance (Rf)= Vf /If …ohms.
Where Vf, If are voltage and current values on Forward
characteristics.
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12. Reverse Resistance:
Static resistance = Vr /Ir …ohms
Where Vr, Ir are voltage and current values on Reverse
characteristics.
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13. Forward bias
Reverse Bias
IF(mA)
IR(uA)
VF(V)VR(V)
Cutin voltage
Breakdown voltage
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