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Basic electronics Module pn junction to digital electronics, Slides of Basic Electronics

Adikavi Nannaya University Basic Electronics

Basic electronics Module pn junction to digital electronics

Typology: Slides

2020/2021

Available from 09/30/2021

Rao-ram 🇮🇳

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Course Content

•Overview of semiconductors

•PN Junction diode

•I-V characteristics of PN diode

•Application of PN junction diode

•Zener diode

•Bipolar junction transistor (BJT) operation

•I-V characteristics of BJT

•Application of BJT

•Operational Amplifier (OPAMP)

•Oscillators

•Digital electronics

Partial preview of the text

Download Basic electronics Module pn junction to digital electronics and more Slides Basic Electronics in PDF only on Docsity!

Course Content

Overview of semiconductors
PN Junction diode
I-V characteristics of PN diode
Application of PN junction diode
Zener diode
Bipolar junction transistor (BJT) operation
I-V characteristics of BJT
Application of BJT
Operational Amplifier (OPAMP)
Oscillators
Digital electronics

Historical background of electronics

Electronics Historical background 1895  First vacuum tube rectifier (diode) 1947  First solid state transistor at Bell labs, USA 1995 ---- 100 years Electronics 1997  Pentium……. 50 years of Transistor Diode  PN junctions in semiconductor Germanium 1947  PNP ,NPN transistor  Field effect transistor (FET) 1960 - 64  Integrated circuit

Introduction to Semiconductors

Semiconductor is the class of material where the conductivity of the material can be controlled to vary a large order of magnitude Ohm’s law: I = V / R J =  E  (conductivity) = 1 /   = R A / L  = 10 - 4 - 10 - 6  - cm (metal)  = 10 - 4 - 10 12  - cm (semiconductors)  = 10 12  - cm (insulators) Temperature dependence: Metals: R increases at higher T Semiconductors: R reduces at higher T

Classification of Semiconductor

Semiconductor Elemental compound: Si, Ge Compound Semiconductor : III-V GaAs, InP II-VI CdTe IV-IV SiC Not all the combinations possible because of lattice mismatch etc.. Alloys : Si 1 - x Gex Image source: Google images^9

Bond model of an intrinsic semiconductor

Valance electrons - Outermost electrons in orbital concepts - Easiest to break off from the nucleus - Participate in the chemical reactions
Why there are electrons/holes?
Why the temperature coefficient of the resistivity of semiconductor is – ve for certain range of the temperature?
You can get rough idea of the concentration of the carrier ( electron/hole) of the semiconductor

Atomic structure

Ge Si Covalent bonding of Silicon atoms Reference: Electronic devices and circuits by Boylestad Silicon (Si) atomic number:14 1S 2 2S 2 2P 6 3S 2 3P 2, Band gap of Si=1.12eV 12

Bond Model of Electrons and Holes

Si atoms connected with two dots represent the two electrons in the covalent bond
At absolute zero temperature there are no free electrons for the conduction

Eg (Bond energy for Si-Si covalent bond) for Si at 300K =1.1eV Average thermal energy of particles at 300K =26meV E = KT, where K= Boltzmann constant and Temperature Number of particles required to break Si-Si bond= 1.1eV/0.026eV ~ 42 Suppose the probability a particle collide with atom is A (probability) Probability of such an event is =A 42 Let us take A=0.9 then Probability= (0.9) 42 n i at room temperature for Si is around 10 10 cm

- 3 So in this case A 42 = 10 /5x 22 =1/5x 12

GE108- Basic Electronics

Intrinsic Semiconductor

Ref: Sedra & Smith 2 - D representation of Silicon crystal at 0K

At 0K (sufficiently low temperature) all the covalent bonds are intact
No electrons available to conduct electric current
Semiconductor behaves as an insulator 2

Some electrons recombine with the holes this process is called as recombination
Recombination rate (R) is proportional to the number of free electrons and holes
Generation rate (G) is strongly dependent on the temperature
At thermal equilibrium condition R=G So n=p=n i Where n i (intrinsic carrier concentration) is the number of free electrons and holes in a unit volume of intrinsic Si at a given temperature

𝒊

𝟑/𝟐 𝒆 −𝑬𝒈/𝟐𝑲𝑻 B is a material dependent parameter; for Si, B=7.3x 15 cm

3 K - 3/ T is the temperature in Kelvin Eg is the band gap energy; for Si Eg=1.12eV at room temperature K is the Boltzmann constant (8.62x
5 eV/K) Mass action law Product of free electrons and holes concentration is equal to the n i 2 . n.p=n i 2 At room temperature n i for Si =1.5x 10 cm
3

P-type extrinsic semiconductors

Acceptor (Boron, In ..) impurity which has vacancy of one electron and accept one electron
Acceptor concentrations is N A , which is order of 10 16 - 10 20 cm - 3
N A >> n i
Free hole concentration p p

≈ N

A For p-type semiconductor p p

n p =n i 2 n p =n i 2 /N A Si crystal doped with trivalent element Ref: Sedra & Smith

If N D

- N

n i then it is n type semiconductor n > N D

– N

A p= n i 2 /n For N D

>> N

A then n=N D and p=n i 2 /N D

If N A

- N

p i then it p type semiconductor p > N A

– N

D n= n i 2 /p, for N A

>>> N

D then p= N A and n=n i 2 / N A

Basic electronics Module pn junction to digital electronics, Slides of Basic Electronics

Related documents

Partial preview of the text

Download Basic electronics Module pn junction to digital electronics and more Slides Basic Electronics in PDF only on Docsity!

Course Content

Historical background of electronics

Introduction to Semiconductors

Classification of Semiconductor

Bond model of an intrinsic semiconductor

Atomic structure

Bond Model of Electrons and Holes

GE108- Basic Electronics

Intrinsic Semiconductor

P-type extrinsic semiconductors

≈ N

- N

– N

>> N

- N

– N

>>> N