wu5c15 by Adel Khamis

8/14/2019 wu5c15 by Adel Khamis

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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.

Work Sheet 2007/2008


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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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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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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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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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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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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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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.


N P

P N


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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.


P PN


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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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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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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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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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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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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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2. AND gate:

Consists of a transistors

with emitter,

act as .

Contain inputs (A, B) and output.



Its truth table is:



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Input

A B

Output

3. OR gate:

Consists transistors connected in

, act as .

Contain inputs (A, B) and

output.



Its truth table is:

Input

A B

Output



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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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4. Very Large Scale integration (VLSI): each chip contains

transistors.

5. Ultra large scale integration (ULSI): each chip greater than

transistors.


wu5c15 by Adel Khamis

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