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8/14/2019 wu5c15 by Adel Khamis
1/19
Unit Five -157- Chapter Fifteen
Introduction to Modern Physics
Modern Electronics
Overview:
There is no single field in all walks of life where electronics has no part.
States of electrons:
There are three states of electrons:
Free electrons: such as .
Bound Electrons: .
Electrons inside semiconductor crystal: which consider as free electrons
because , and consider as bounded because
...
Classification of matter:
According to state:
Solid, Liquid or Gas; where the
controls the state.
The molecular distance is controlled by force and
.. force, and that distance is the balanced point between the two
forces.
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Unit Five -158- Chapter Fifteen
According to electric conductivity:
Conductors: which are good conductor to and . (e.g.:
), .. are responsible for electrical conductivity.
Insulators: which are bad conductor to and . (e.g.:
).
Semiconductors: which are insulators theoretically at degree
Kelvin, while their conductivity (increase / decrease) by increase the
temperature (e.g.: ..).
Pure semiconductor:
Silicon is an element from the
group, therefore it has electrons at its
outer shell
Crystal of silicon consists of silicon atoms
bound together in bonds.
At low temperature (0K) all
bonds in the crystal are intact
(unbroken), therefore it consider
as (good conductor / good
insulator).
By increase the temperature some of the bonds are .; therefore,
electrons .. and leave .. in their place.
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Unit Five -159- Chapter Fifteen
Both of electrons and positive holes in case of .., electrons
fill the holes and other bonds break to create more of free electrons and
positive holes.
By increase the temperature the number of broken bonds (increases /
decrease) tell a certain value where the rate of break the bonds (smaller
than / equal to / greater than) the rate of filling holes and this case called
thermal equilibrium.
What is meant by:
Thermal equilibrium:
Doping:
It is .
...
n-type:
By adding of element Phosphorus (P) or Antimony (Sb) it
replace silicon atom.
Since the .. element has .. electrons at the outer
shell therefore it use only . electrons to form
bonds with the neighboring Silicon, while there is a free electron act as
charge carrier.
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Unit Five -160- Chapter Fifteen
The total electric charge of the crystal is .. where
....
Since the . element act as new source of free electrons
therefore it called . atom. (N.)
The number of free electrons (n) becomes (greater than / equal to /
smaller than) that of positive holes (p). by the concentration of
pentavalent element.
n=+.
p-type:
By adding of element Aluminum (Al) or Boron (B) it
replace silicon atom.
Since the . element has .. electrons at the outer
shell therefore it form only .. bonds with the neighboring
Silicon, while the fourth bond has lack of electron, which called
., that positive hold consider as charge carrier.
The total electric charge of the crystal is .. where
..
Since the . element act as source of holes therefore it called
. atom. (N..)
The number of free electrons (n) becomes (greater than / equal to /
smaller than) that of positive holes (p). by the concentration of trivalent
element.
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Unit Five -161- Chapter Fifteen
p=.+
Item n-Type p-Type
Valence of doping material . ..
Doping material .... ...
Charge carrier ..
Charge of the crystal .
Relation between free (e)
and Holes
..
Generally:
pn=ni2
Where:
ni: is ..
This law is called mass action law.
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Unit Five -162- Chapter Fifteen
In case of n-type:
n=ND
...........
..........=p
In case of p-type:
p=NA
...........
..........=n
Example:
If electron or hole concentration in pure silicon is 1x1010 cm-3, phosphorus is
added at a concentration of 1012 cm-3, calculate the concentration of electrons and
holes in this case. Is this silicon N-type or P-type?
..
Electronic Components and Devices:
It is the building blocks for all electronic systems.
Some of it is simple: e.g.: .
Others are complex: e.g.: .
It made of semiconductors, and that semiconductors are sensitive to
such as . and , therefore it is used as sensors to measure
the external stimuli, e.g.: intensity of light,
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Unit Five -163- Chapter Fifteen
pn-junction (diode):
It is consists of a single crystal of
semi-conducting material, which
contains two adjacent regions one of
type and the other is ..type.
Some electrons from the . region move
across the junction towards the p-type, and some
.. move across the junction towards the n-
type.
As a result the middle area contains no charge carrier
(nether electrons nor holes), this area is called
region or depletion region.
Due to .. between the two regions, electric field is
created from p-type to n-type causing back current to pass which called
drift current, opposite in direction to the diffusion current.
At equilibrium the back current (drift current) is in magnitude
and in direction to the forward current (diffusion current),
and the net current is equal ...
Types of connection:
There are two types of connection with the electric
source, forward bias connection and backward bias connection.
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Unit Five -164- Chapter Fifteen
Forward connection:
The positive pole of the battery is connected
to .-type, while the negative pole is
connected to the .-type.
Holes move (towards / away from) the positive electrode of the battery
and electrons move (towards/ away from) the
negative electrode of the battery (increasing/
decreasing) the transition area.
The electric field due to the battery will be in the (same / opposite)
direction to the electric field due to pn-junction.
(High / No) current passes through the junction.
Backward connection:
The positive pole of the battery is connected
to -type, while the negative pole is
connected to ..-type.
Holes move (towards / away from) the negative electrode of the battery
and electrons move (towards / away from) the positive electrode of the
battery (increasing / decreasing) the
transition area.
The electric field due to the battery will
be in the (same / opposite) direction to
the field due to pn-junction.
(High / No) current passes through the junction.
Work Sheet 2007/2008
N P
P N
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Unit Five -165- Chapter Fifteen
Usage of the N-P junction:
It used to the AC, passing half cycles only of the current.
In the half cycle when connection is .. and
the current .. through the junction, while in
the other half the connection will be and
. current pass.
It is used also to convert the AC current into
DC current.
Transistor:
It consists of . regions, the middle one is thin and made of a type
(.) and the other two regions form
the other type (.. and ..).
It means that there are two kids of
transistors P-N-P and N-P-N, both give the same functions.
It is connected to the power supply making two circuits, emitter circuit
and collector circuit.
The emitter circuit connects in . direction, and the collector
circuit connects in ...
The current passes from the emitter to the collector through ., and
because of the . of the base most of the current pass
from the emitter to the collector.
Work Sheet 2007/2008
P PN
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Unit Five -166- Chapter Fifteen
Since the base contains holes therefore some of is used
to fill that holes which lead to small portion of lost to recombination (e).
Where:
(e): is the
The collector current can be calculated from the relation:
IC =
The base current can be calculated from the relation:
IB = ..
IB = ..
IB = (.. - )
The ratio between collector current
to the base current (e), which called
current gain can be calculated from the
relation:
.........
.........=e
.....................
....................=e
( )e
ee
=
1
Since the base is very thin therefore the recombination value (e) is
, and that lead to current Gain (e) is ..
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Unit Five -167- Chapter Fifteen
This leads the transistor to act as current amplifier which called transistor
action.
Example:
A transistor has e = 0.99. Calculate e then calculate the collector current if
the base current is 100A.
..
Transistor as a switch:
The voltage of battery is equal to the summation of voltage of the circuit
components.
Vcc = V. + V
Vcc = V + I. R.
From the equation by increasing the collector current, then the potential
difference between emitter and collector (increase / decrease) [it reaches
0.2 V], and vice versa.
Switch on:
By connecting high signal (positive signal) to the base, the collector
current will (increase / decrease).
Therefore ICRC will (increase / decrease), which consider as switching (on
/ off)
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Unit Five -168- Chapter Fifteen
and VCE will (increase / decrease).
By considering Base as input, collector as output, and the emitter as
ground, therefore increase the input voltage leads to (increase / decrease)
the output voltage.
It means that the transistor act as inverter.
Switch off:
By connecting low signal [negative signal] to the base, the collector
current will (increase / decrease).
Therefore ICRC will (increase / decrease), which consider as switching (on
/ off)
and VCE will (increase / decrease).
By considering Base as input, collector as output, and the emitter as
ground, therefore decrease the input voltage leads to (increase / decrease)
the output voltage.
It means that the transistor act as inverter.
Analog and digital electronics:
Analog Digital
Transmitted .. Transmitted in form of .........
Included the . Does not include the .
Work directly with sender and receiver .. converter is used
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Unit Five -169- Chapter Fifteen
devices at sender device.
converter is used
at receiver device
Dismal system:
Deal with .. digits: .......
Base and power . . . .
Value of column . . . .
Number 0 2 5 7
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Unit Five -170- Chapter Fifteen
The number can be calculated as:
Digit Column value Value
7 .. .
5 . .
2 .. .
Therefore the total value of the number is ..+..+.. = .
Binary system:
Deal with . digits: .. and ..
Base and power .
Value of column .
Number 0 1 1 0
The number can be calculated as:
Digit Column value Value
0 ..
1
1
0
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Unit Five -171- Chapter Fifteen
Therefore the total value of the number is ++ =
Convert from binary to dismal:
Convert (47)10 into binary
.. .. .. .. .. .. 47
.. .. .. .. .. ..
Therefore (47)10 = (101111)2
Logic Gates:
1. Inverter (Not gate):
Consists of . act as ...
Contain . input and ..
output.
Its symbol as in figure:
Its equivalent circuit as in figure:
Its truth table is:
Input Output
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Unit Five -172- Chapter Fifteen
2. AND gate:
Consists of a transistors
with emitter,
act as .
Contain inputs (A, B) and output.
Its symbol as in figure:
Its equivalent circuit as in figure:
Its truth table is:
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Unit Five -173- Chapter Fifteen
Input
A B
Output
3. OR gate:
Consists transistors connected in
, act as .
Contain inputs (A, B) and
output.
Its symbol as in figure:
Its equivalent circuit as in figure:
Its truth table is:
Input
A B
Output
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Unit Five -174- Chapter Fifteen
Electronic circuits:
It is number of electronic components connected tighter in a closed path.
The electronic circuits classified into:
1. Discrete circuits: where it consists of .
2. Integrated circuits: where .
The electronic components classified into:
1. Passive components: (e.g: ..)
2. Active components: (e.g.: ..)
Moors law:
..
Electronic chips can be classified into:
1. Small scale integration (SSI): each chip contains transistors.
2. Medium Scale integration (MSI): each chip contains
transistors.
3. Large Scale integration (LSI): each chip contains transistors.
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Unit Five -175- Chapter Fifteen
4. Very Large Scale integration (VLSI): each chip contains
transistors.
5. Ultra large scale integration (ULSI): each chip greater than
transistors.
Work Sheet 2007/2008