Class 12 Physics | Semiconductor Electronics: Material Devices and Simple
Circuits
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,Class 12 Physics | Semiconductor Electronics: Material Devices and Simple
Circuits
Semiconductor Electronics:
Material Devices and Simple
Circuits
Notes
www.learnohub.com
,Class 12 Physics | Semiconductor Electronics: Material Devices and Simple
Circuits
Introduction
We know that earlier electronic devices were made up of vacuum tubes or
valves
Vacuum tubes or Valves:
• The evolution of vacuum tubes started with diode and proceeded to triode,
tetrode and pentode
• Valves control the flow of electrons; In diodes, there were two electrodes –
cathode and anode
• Similarly, triode had three electrodes – cathode, grid and anode; tetrode
had four electrodes – anode, two grids and cathode; pentode had five
electrodes –anode, three grids and cathode
• Generally in vacuum tubes, the electrons are produced by heating the
cathode using low tension battery; The vacuum helps in electron not losing
its energy by collision with air molecules in the way
• However, the vacuum tube devices had some disadvantages and they are
o Bulky
o Operate at high voltages
o Consume more power
o Have limited life
o Low reliability
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, Class 12 Physics | Semiconductor Electronics: Material Devices and Simple
Circuits
Diodes and transistors
• Next came the discovery of semiconductor junction, namely, junction diode
and transistors
• These replaced the vacuum tubes or valves
• The advantages of semiconductor devices are
o Small in size
o Operate at low voltages
o Consume small power
o Long life
o High reliability
• Though the above advantages are present, the circuits consisting of
transistors were still bulky, less shock proof
• Hence, it led to the discovery of integrated circuits which is a major
revolution in the electronic industry
Example – The earlier generation television and computer monitors were very
bulky as they were based on the principle of vacuum tubes; now days, we have
LCD (Liquid Crystal Display) monitors which support solid state electronics
Classification of metals, semiconductors and insulators
On the basis of conductivity
The conductivity of a material indicates whether they can be classified as
metals, semiconductors or insulators
The electrical conductivity is expressed as σ whereas the reciprocal of
conductivity is resistivity ρ = 1/σ
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Circuits
www.learnohub.com
,Class 12 Physics | Semiconductor Electronics: Material Devices and Simple
Circuits
Semiconductor Electronics:
Material Devices and Simple
Circuits
Notes
www.learnohub.com
,Class 12 Physics | Semiconductor Electronics: Material Devices and Simple
Circuits
Introduction
We know that earlier electronic devices were made up of vacuum tubes or
valves
Vacuum tubes or Valves:
• The evolution of vacuum tubes started with diode and proceeded to triode,
tetrode and pentode
• Valves control the flow of electrons; In diodes, there were two electrodes –
cathode and anode
• Similarly, triode had three electrodes – cathode, grid and anode; tetrode
had four electrodes – anode, two grids and cathode; pentode had five
electrodes –anode, three grids and cathode
• Generally in vacuum tubes, the electrons are produced by heating the
cathode using low tension battery; The vacuum helps in electron not losing
its energy by collision with air molecules in the way
• However, the vacuum tube devices had some disadvantages and they are
o Bulky
o Operate at high voltages
o Consume more power
o Have limited life
o Low reliability
www.learnohub.com
, Class 12 Physics | Semiconductor Electronics: Material Devices and Simple
Circuits
Diodes and transistors
• Next came the discovery of semiconductor junction, namely, junction diode
and transistors
• These replaced the vacuum tubes or valves
• The advantages of semiconductor devices are
o Small in size
o Operate at low voltages
o Consume small power
o Long life
o High reliability
• Though the above advantages are present, the circuits consisting of
transistors were still bulky, less shock proof
• Hence, it led to the discovery of integrated circuits which is a major
revolution in the electronic industry
Example – The earlier generation television and computer monitors were very
bulky as they were based on the principle of vacuum tubes; now days, we have
LCD (Liquid Crystal Display) monitors which support solid state electronics
Classification of metals, semiconductors and insulators
On the basis of conductivity
The conductivity of a material indicates whether they can be classified as
metals, semiconductors or insulators
The electrical conductivity is expressed as σ whereas the reciprocal of
conductivity is resistivity ρ = 1/σ
www.learnohub.com
