AUTOMOTRIZ ELECTRONICOS
AUTOMOTRIZ ELECTRONICOS
Published by Chonan Technical Service Training Center
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Chonan Technical Service Training Center
AUTOMOTRIZ ELECTRONICOS
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Chonan Technical Service Training Center
AUTOMOTRIZ ELECTRONICOS
FOREWORD This service-training booklet has been prepared for service technicians of authorized distributor to familiarize them with vehicle basic electronic. It is our intention to increase the level of skill and knowledge of service personnel to enable effective and efficient problem diagnosis and repair.
December. 2003 Printed in Korea Published by Chonan Technical Service Training Center
ⓒ copyright by Hyundai Motors All right reserved. Chonan Technical Service Training Center http://training.hmc.co.kr
[email protected]
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AUTOMOTRIZ ELECTRONICOS
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AUTOMOTRIZ ELECTRONICOS
CONTENTS 1. General ··········································
7
8. Thermistor ··································· 45
2. Compositions/essence of electricity ··
8
8.1 NTC type ··········································· 45
3. Conductor & nonconductor ··············
9
8.2 PTC type ············································ 46
4. Semiconductors ······························ 11
9. Photoconductive cell ························· 47
4.2 Semiconductor material ························· 12
10. Piezo-electric element ···················· 48
4.3 Classification of semiconductor ·············· 13
11. Hall effect ··········································· 49
5. Diode ······················································· 17
12. Integrated circuit ······························ 51
5.1 Diode general ······································· 17
12.1 Integrated circuit general ··················· 51
5.2 Diode usage & symbol representation ····· 17
12.2 Analog I.C ································· 52
5.3 Diode operation ····································· 18
12.3 Digital I.C ········································· 53
5.4.Characteristic of diode ··························· 20
12.4 Various logic circuits ························· 54
5.5 Rectification operation of diode ············ 21
13. Microcomputer ·································· 59
5.6 Example of diode use in automobile ······· 23
14. To understand electronic circuit ····· 63
5.7 Diode check method by using a m-meter
25
APPENDOX ············································ 67
6. Special type of semiconductor diode · 26 6.1 Zener diode ·········································· 26 6.2 Photo diode ··································· 28 6.3 LED (Light emitting diode) ······················ 29
7. Transistor ··············································· 31 7.1 What’s transistor? ···························· 31 7.2 Basic operation of transistor ··················· 32 7.3 Judgment of good/bad transistor
········· 42
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AUTOMOTRIZ ELECTRONICOS 1. General Today in automobile there are essentially used application fields of electricity and electronic beginning from switch for simple on /off of lamp to many equipments of engine management system (EMS ) , antilock brake system (ABS ) , transmission control system (TCS ) , airbag, instrumentation system, body electrical system (BCM), etc. requiring microcomputer control. Because of use of so many sophisticated electrical equipments and electronic parts, there come forth also many electronic defects in comparison to traditional mechanical defects as for car trouble causes. Accordingly learning the basic knowledge of electricity and electronic seems exigent subject for automobile maintenance and service. . Here it is hoped to become opportunity to understand basic principle and to learn how they apply in automobile, apart from the complicated structure or any academic theoretic. And it is hoped to be a little help in more efficient maintenance and trouble repair..
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AUTOMOTRIZ ELECTRONICOS 2. Compositions and essence of electricity Every material is composed of molecules each of which is in turn chemically composed of aggregates of atoms. Example: water molecule (H2O) = two hydrogen atoms (H2) + one oxygen atom (O) M Orbit Electron
K Orbit
Proton Neutron
Atomic nucleus L Orbit
Atom relationship model As the above figure, electrons are quickly turning around nucleus in conformity with respective orbits as the earth and planets are turning around sun . Only a certain number of electrons can exist in each electron orbit (K: 2, L: 8, M: 18, . . . ) while each element has its characteristic number of electrons (e . g . hydrogen 1, carbon 6, oxygen 8, . . . ). Generally nucleus has positive electricity (+) and electron has negative electricity (-) while these two have mutually attractive character so that atom becomes electrically neutral (positive electricity quantity = negative electricity quantity).
Because attractive force from atomic nucleus to electrons
of outermost orbit (valence electrons) is the weakest , these electrons are easy to escape from orbit due to external stimulus (heat , electricity, light , ...) and may move to other orbit , got out of orbit are called free electrons which are essence of electricity. electrons directly becomes electric current .
These electrons
Movement of these free
Namely, it means that movement of these free
electron started signifies that electric current flows,
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AUTOMOTRIZ ELECTRONICOS 3. Conductor & nonconductor If materials are electrically classified , they may be divided into conductor which transmit electricity well, nonconductor which do not transmit electricity and semiconductors in middle between the two while these characteristics are determined by electronic configuration according to atomic structure of material . 1) Conductor : where electricity flows well Here fall most metals where free electrons may well move in the interior of material . Order of good conductance of electricity : silver copper gold aluminium tungsten zinc nickel .... 2) Nonconductor : where electricity does not flow well It is called insulator where free electron is not easily generated e . g . ceramics, glass, rubber, plastics, wood etc . 3) Semiconductor : which has medial characteristics between conductor and nonconductor Here fall silicon (Si), germanium (Ge), selenium (Se) etc . which are used as raw material of electronic part. As for automobile wiring, multistrand type is contained inside a clothing of cord where copper (alloy) is mainly used as stuff material . load, continuity, temperature etc .
Cord thickness is determined by electric current value,
The larger the electric current , the longer the cord and the
longer the electric current flow time , the thicker the electric cord shall be . General Specification Table Area (mm )
Strand Diameter
No. of Strands
Electric Wire OD
0.5
0.32
7
2.2
Allowable Current (A) 9
0.85
0.32
11
2.4
12
0.5 sq (Allowable
1.25
0.32
16
2.7
15
electric current =
2
0.32
26
3.1
20
9 A)
3
0.32
41
3.8
27
5
0.32
65
4.6
37
8
0.45
50
5.5
47
15
0.45
84
7.0
59
20
0.8
41
8.2
84
9
0.32 mm
2.2 mm
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AUTOMOTRIZ ELECTRONICOS
MEMO
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AUTOMOTRIZ ELECTRONICOS 4. Semiconductor 4.1 What is semiconductor? In material, there are conductors easy for electric current to flow and nonconductor difficult for current to flow by the electronic property.
Semiconductor denotes material of medial property
between conductor and insulator. Namely, here electric current is neither easy to flow as in conductor nor difficult as in nonconductor.
Semiconductor is material that has such peculiar
electric property. So semiconductor is material that has medial type character between conductor and nonconductor.
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AUTOMOTRIZ ELECTRONICOS 4.2 Semiconductor material The specific resistance of copper used as electric conductor is 10 -6 Ωcm that is lowest and even the specific resistance of Ni-Cr used as electric resistance wire is 10-4 Ωcm while these materials are called conductors because they conducts electricity well .
If specific resistance is more than 1010
Ωcm then little electricity is conducted there so that such material is used as insulator. Meanwhile material in between such conductor and insulator, not belonging to conductor and nonconductor, are called semiconductor where belong germanium and silicon used in manufacturing the diode and transistor.
State
Specific Resistance
Material
10-6
Silver, copper Platinum
10
-4
10
-2
Conductor
Nichrome Carbon electrode
Pyrite 1 Germanium 102 Silicon 104 106 10 Semiconductor
Copper dioxide
8
1010
Bakelite
1012 1013
Mica , diamond
1014 1015
Glass
1016 1018
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Quartz glass
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AUTOMOTRIZ ELECTRONICOS Semiconductors play role of conductor or nonconductor according to specific condition (relationship between voltage, electric current , temperature etc . ).
The main elements that are most frequently
used are silicon (Si) and germanium (Ge) while such conductor of high purity is called as intrinsic semiconductor.
Silicon and germanium respectively have four electrons on outermost orbit .
Namely in their respective crystal structures, the form becomes that each atom shares its own four electrons with its partner atom.
Because of such covalent bond, the material becomes an electric
insulator and has little electrical utilization value so that it cannot independently be used as semiconductor.
Therefore it is used as a form of impurity semiconductor by adding small
proportional quantity of other element atoms to these intrinsic atoms of valence 4. 4.3 Classification of semiconductor Semiconductor is largely constituted of two forms. Here are iintrinsic semiconductor that does not utterly contain impurity in material crystal and impurity semiconductor that is added of specific impurity material into intrinsic semiconductor in order to improve conductivity. Generally diode and transistor belong to this impurity semiconductor. And this impurity semiconductor is also classified into two according to role of added impurity material . Roles of impurity material are to increase in semiconductor the number of -
Increase free electron of semiconductor inside
-
Increase hole of semiconductor inside
Therefore among impurity semiconductors, that added of impurity to increase the number of free electron are called negative type semiconductor while that added of impurity to increase the number of hole are called positive type semiconductor. Outer block Orbit
S
i Si
S
S
S
i
i
i
S
i
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AUTOMOTRIZ ELECTRONICOS 4.3.1 Intrinsic Semiconductor ▷ This is intrinsic semiconductor containing no impurity material at all in its crystal structure . ▷ Purity of intrinsic semiconductor has been refined about 99.999999999 % (over ten-nine) with 11 nine. ▷ For example germanium and silicon belong to this kind . 4.3.2 Impurity semiconductor ▷ This is impurity semiconductor added of specific impurity material into intrinsic semiconductor to improve conductivity. ▷ General semiconductors of diode or transistor belong to this impurity semiconductor. ▷ Classification of impurity semiconductor a. N type semiconductor is that added of impurity to increase number of free electron in semiconductor. b . P type semiconductor is that added of impurity to increase number of hole in semiconductor. 1) P Type Semiconductor This is made by adding the material (Ga : gallium ; In : gallium ; B : boron ) having three valence electron in intrinsic semiconductor.
Though silicon has four outer layer electron, if these two kinds
of material meet each other, then silicon atom from these two kind of atoms cannot share one electron so that electric current can flow easier while this vacancy in octet is called hole.
And it is
called P (positive) type semiconductor because it assumes positive (+) electricity by electron deficiency. When voltage is applied, electron fills the hole site so that the hole continuously moves down, electric current is said to flow by means of hole in P type semiconductor.
Hole Structure of “P” type semiconductor 14
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AUTOMOTRIZ ELECTRONICOS 2) N Type semiconductor This is made by adding the material ( P : phosphorus ; As : arsenic ; Sb : antimony ) having five outermost layer electron in intrinsic semiconductor. If element of valence 5 is added to bind with silicon then one electron remains as surplus in octet so that electric conduction may be accomplished easier by means of free activity of this remainder electron. And it is called N (negative) type semiconductor because it assumes negative (-) electricity. Electric current flows by means of electron in N type semiconductor (carrier : electron ) .
Superfluity electron
Structure of “N” type semiconductor 3) P-N Junction If P type semiconductor and N type semiconductor are chemically bonded with each other, there is made portion where carrier does not exist as hole and free electron are bonded together at narrow part of junction surface. This junction surface is called depletion layer while semiconductor bonded thus is called PN junction semiconductor or diode.
Accordingly there exists electric charge of
different polarity from each other on either side of depletion layer and there is generated a little amount of electric potential difference which is called electric potential barrier.
P
N
Electron Hole
Depletion layer
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AUTOMOTRIZ ELECTRONICOS
MEMO
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AUTOMOTRIZ ELECTRONICOS 5 Diode (Diode for rectifier circuit) 5.1 Diode general Diode is semiconductor part substance flowing the electric current always in only one direction . to say, semiconductor is called as such because it has intrinsically this kind of property.
As
Although
transistor is also a kind of semiconductor, diode specifically purports thus that electric current shall flow always in only one direction .
Silicon is most frequently used as semiconductor material
whereas besides there are used also germanium and selenium for this purpose
Anode(－)
Cathode(＋)
5.2 Diode usages and symbol representation Main function of diode is to rectify electric current to flow it always in only one direction.
But it is
also used in many other functions so that main functions may be summarized as follows : -
Usage as electric current rectifier to change the alternating current to the direct current in electric supply facilities
-
Use as detector to take out signal from radio frequency
-
Usage in switching to control electric current ON/OFF
-
Prevention of backward current flow
-
Usage in protective circuit
Besides it is used in variety of wide range according to diode sort and usage.
Anode Diode symbol
Cathode Diode Polarity
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AUTOMOTRIZ ELECTRONICOS 5.3 Diode operation § Forward diode for forward bias § Forward diode for backward bias 5.2.1 Forward diode for forward bias Diode has form to have connected terminals on both sides of P-N junction semiconductor to have characteristics to flow electric current always in only one direction . In forward direction as in figure if positive (+) voltage is applied at P type semiconductor and negative (-) voltage is applied at N type semiconductor, hole and electron repulse to electric source so that electric potential barrier is lowered and also depletion layer is narrowed.
Consequently
hole and electron may move to each other across junction surface. Accordingly electric current flows by movement of hole and electron . Depletion layer
Current flow
P
N
Forward direction circuit of diode Lamp turns on because diode has been connected in forward direction in circuit below. Anode(＋) Battery
Cathode(－)
Lamp ON
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AUTOMOTRIZ ELECTRONICOS 5.2.2 Backward diode for reverse bias This time let us in reverse direction apply negative (-) voltage at P type semiconductor and positive (+) voltage at N type semiconductor. Then hole of P type semiconductor is attracted to negative (-) side of electric supply while electron of N type semiconductor is attracted to positive (+) side of electric supply.
Consequently electric potential barrier is heightened and accordingly depletion layer is also
widened so that electron movement cannot arise between the two kinds of semiconductor. As the result , electric current does not flow Depletion layer
No current flow
P
N
< Occasion that supply backward voltage / Electric current is not flowing >
Backward direction circuit of diode Lamp turns off because diode has been connected in backward direction in circuit below.
Cathode(－) Battery
Anode(＋)
Lamp Off
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AUTOMOTRIZ ELECTRONICOS 5.4 Characteristic of diode It can be seen that , when forward voltage is gradually increased from 0 V, electric current abruptly flows if a certain voltage is reached.
Namely electric current only becomes to flow if voltage is
applied over about 0.6~0.7 V (Ge diode: 0.3~0.4 V).
And if backward voltage is applied, electric
current does not flow up to some voltage but abruptly flows at voltage over some definite value. Voltage at this instant is called breakdown voltage. Namely diode is broken down if it is connected in reverse direction and voltage above breakdown voltage is applied. ID(mA) Forward direction
Breakdown voltage VD(Volt) Silicon: 0.6~0.7 volt Backward direction Characteristic curb of diode Voltage-Current characteristicsGraph of Forward Voltage-Current Characteristics Diode : Diode Current Flow to Applied Voltage When forward bias voltage is applied below 0.7 V → micro current flows : diode does not operate When forward bias of threshold voltage of 0.7 V is applied → diode operation current flows : diode operates
I
• [mA] •60 •40
Diode forward direction Spiritual enlightenment point
•20
•0.2
•0.4
•0.6
•0.8
•1.0• Volt
Forward direction voltage characteristic of silicon junction diode
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AUTOMOTRIZ ELECTRONICOS 5.5 Rectification operating of diode An alternating current signal may be rectified to a direct current by using characteristic of electric current in diode to flow always in only one direction.
Rectifier circuit may largely be classified into
half wave rectifier circuit and full wave rectifier circuit . 5.5. 1 Half -wave rectifier circuit When applying an alternating current to the circuit , at moment when positive (+) side signal comes in, electric current flows in forward direction, but at moment when negative (-) side signal comes in, electric current does not flow because it becomes the reverse direction. This kind of circuit to flow electric current for only one side is called half wave rectifier circuit .
Volt
A.C Time
Diode
Input Voltage
A.C
IR
Output Voltage
Input voltage
R VR = D.C Volt
D.C Time
Output voltage Half -wave rectifier
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AUTOMOTRIZ ELECTRONICOS 5.5.2 Full-wave rectifier circuit Next for other device also when applying an alternating current to the circuit , electric current flows through D1 and D4 during moment of positive (+) half cycle period of alternating current signal while the current flows through D2 and D3 during moment of negative (-) half period. This kind of circuit to flow electric current for both of half periods is called full wave rectifier circuit . ( *Although particularly here is represented a full wave rectifier using a bridge, there are also full wave rectifier circuit using the center tap of transformer, voltage doubler rectifier circuit etc . )
Volt Time D2
Input Voltage
D1
V= A.C D3
D4
V= D.C
R
Volt Time Output Voltage
Bridge circuit full-wave rectifier
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AUTOMOTRIZ ELECTRONICOS 5.6 Example of diode use in automobile ◐ Alternator rectifier AC voltage generated at stator coil is transformed to DC voltage across the diode Voltage of A : DC 13.7 volts Voltage of B: AC Pick-to-Pick voltage 13.7 volts × 2 = 27.4 volts AC voltage of Pick-to-Pick voltage of B is outputted only in + voltage after passing the diode so that only 1/2 voltage of 27.4 V is outputted. Namely AC voltage after passing the forward diode is outputted in accordance with vanishing of – voltage. To Battery
From fusible link
From charging lamp
A
B
Alternator internal circuit
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AUTOMOTRIZ ELECTRONICOS ◐ Diode installed in relay to prevent surge voltage
A B A
C Battery
M
Motor
Relay
Controller ㄱ 1) If power transistor of controller turns on, then the relay turns on . 2) Motor operates as the relay turns on . 3) When power transistor turns off in controller, a high surge voltage about 80volts is instantaneously generated between A and B according to Lenz law so that it becomes + voltage. 4) If this surge voltage of 80 volts flows in the controller, the controller may be damaged . 5) In order to prevent this problem , diode is installed in the relay so that the surge voltage generated between A~B shall digress in direction from A to C across diode to be extinguished for controller damage prevention . ◐ Diode connection in forward direction and reverse direction in electric circuit Forward bias direction connection Anode(＋) Battery
Cathode(－)
Lamp ON
Backward bias direction connection Cathode(－) Battery
Anode(＋)
Lamp Off
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AUTOMOTRIZ ELECTRONICOS 5.7 Diode check method by using a multi-meter If we had understood that diode is PN junction semiconductor where electric current would flow in case of forward direction but would not flow in case of backward direction, we can judge it whether good or bad in accordance with the following. 5.7.1 How to check by using a Digital Multi-Meter 1) Select resistance or diode mode for the select switch of digital meter. 2) It is normal if resistance value is small when red lead wire has been connected to diode anode (+) and black lead has been connected to cathode (-). 3) And it will be rather good if resistance value is higher when connected inversely. ① Short condition : normal if value is near 0 ohm when measuring in forward direction a n d backward direction . ② Open condition : normal if value is near infinity ohm when measuring in forward direction a n d backward direction . When checking by using digital multi meter = Normal condition Anode
++
Cathode
Cathode
-－
Anode
-
+
∞Ω
0 Ω Red lead wire
Red lead wire
Black lead wire
Resistance : ≒ 0 Ω
Black lead wire
Resistance : ∞ Ω
5.7.2 How to check by using an Analog Multi-Meter 1) Select at resistance range × 100 for the select switch of analog multi meter. 2) It is normal if resistance value is small when black lead wire has been connected to diode anode (+) and red lead has been connected to cathode (-). 3) And it will be rather good if resistance value is higher when connected inversely. ① Short condition : normal if value is near 0 ohm when measuring in forward direction a n d backward direction .
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AUTOMOTRIZ ELECTRONICOS ② Open condition : normal if value is near infinity ohm when measuring in forward direction a n d backward direction . When checking by using analog multi meter = Normal condition Anode
+
Cathode
Cathode
-
Red lead wire
Red lead wire
Black lead wire
Anode
+ Black lead wire
Resistance : ∞ Ω
Resistance : ≒ 0 Ω
6. Special type of semiconductor diode Diodes are used for a number of purposes. Voltage rectification, voltage regulation, and even light production are some of their various uses. Following is a brief description of some diode type you might encounter. 6.1 Zener diode 1) Zener diode symbol Cathode(－)
Anode(＋)
2) Zener diode characteristic When the diode is forward biased, it acts like reverse diode or a closed switch. However, the zener diode has unique reverse bias qualities that make differ from the typical diode. The zener diode goes in to reverse bias at various voltages. The amount of voltage required for reverse bias varies according to the zener diode selected. Some typical reverse bias voltages are 2.4V, 5.1V, 6.0V, 9.1V, 12.0V, ect. At this point, when the applied voltage increased, the forward current increase.
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AUTOMOTRIZ ELECTRONICOS This small reverse current flows until the diode reaches the zener breakdown point, V2 in figure. At zener breakdown point, the zener diode is able to maintain a fairy constant voltage as the current varies over a certain range. Because of this attribute, the diode provides excellent voltage regulation.
＋
Forward bias
Zener breakdown
region
＋
V2
0
Voltage
Voltage remains constance over large current Reverse range bias
－ Current
Zener diode characteristic
3) Zener diode usage An electronic device that can be used as a voltage regulator is the zener diode. 4) Example of circuit that use zener diode - Zener diode breakdown voltage of circuit below is 12 V. - Supply voltage to controller through C1 in circuit diagram below shall never exceed 12 V. - If supply voltage exceeds 12 V then it is earthed through zener diode. So, because current is extinguished through earth for voltage above 12 Volts any voltage above 12 Volts is not supplied to controller.
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AUTOMOTRIZ ELECTRONICOS C1
Supply Voltage R3 R1
R4
Controller
Condenser
ZD 12Volts
TR
R2 Earth Earth
6.2 Photo diode 1) Photo diode symbol
Cathode(－)
Anode(＋)
2) Photo diode characteristic Electric current flows if lighted on PN junction surface under condition where certain voltage is applied in backward direction. And if light irradiation dose is changed, electric current changes in proportion to the light quantity.
Electric potential barrier is made on PN junction surface and
becomes greater if reverse voltage is applied so as to become a complete insulator.
If light is
shed on PN junction surface under this condition, change arises on the junction surface. Respectively electron and hole are activated by external light energy along with positive (+) ion in N side area and negative (-) ion in P side area .
Hole and free electron separated from
respective ions move along so that electric current gets to flow.
Thus diode is used in light →
electricity transformation circuit . Whence if voltage is maintained constant , electric current flowing in circuit gets proportional to the light quantity received by element .
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AUTOMOTRIZ ELECTRONICOS 3) Example of circuit that use photo diode -
Photo diode has been connected in backward direction in circuit below.
-
If light irradiates on photo diode, then because battery voltage is supplied, the lamp turns on .
-
It is much used as a switching circuit .
Photo diode Battery 12 volts
Lamp
Photo diode circuit
6.3 LED (Light emitting diode) 1) Photo diode symbol
Cathode(－)
Anode(＋)
2) Light emitting diode characteristic This diode is that which illuminates as electric current flows by applying forward voltage at PN junction diode. -
Its characteristics are as follows :
It has longer life and electric power consumption is smaller in comparison to incandescent electric lamp.
-
Response is speedy.
-
It illuminates even with low voltage of 2 ~3 V.
-
Power consumption is small (about 0.05 W ) ,
-
Response of turning on and off is quick (by unit of millionth second).
-
As for illumination color, there are red, green, yellow etc. according to semiconductor material.
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AUTOMOTRIZ ELECTRONICOS 3) Example of circuit that use zener diode - If switch is closed in circuit below, then electric current flows so that LED illuminates. - As for role of resistance, it was used for voltage drop to apply a voltage of 3 V at LED.
LED
9 Volts.
3 Volts Switch
Battery
Photo diode circuit
4) Trip computer display using a LED
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AUTOMOTRIZ ELECTRONICOS 7. Transistor 7.1 What’s transistor? PNP type transistor is that where thin N type semiconductor in a semiconductor crystal has been inserted between two P type semiconductors while NPN type transistor is that where thin P type semiconductor has been inserted between two N type semiconductors. For symbols in semiconductor, E denotes emitter terminal, B denotes base terminal and C denotes collector terminal Each Part Symbol and Sorts of Transistor
Transistor according to association of semiconductor, there are PNP type and NPN type. And, transistor according to usage and type, following name is attached. 2SA××× ----- For high frequency transistor of PNP type 2SB××× ----- For low frequency transistor of PNP type 2SC××× ----- For high frequency transistor of NPN type 2SD××× ----- For low frequency transistor of NPN type
D: For low frequency transistor of NPN type
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AUTOMOTRIZ ELECTRONICOS
P type Collector(C )
N
N
Type
Type
N type Emitter (E)
Collector(C )
P Type
Base (B)
Emitter
P Type
(E)
Base (B)
Collector(C
Emitter
)
(E)
Collector(C
Emitter
)
(E)
Base (B)
Base (B) NPN type transmitter structure & symbol
PNP type transmitter structure & symbol >
7.2 Basic operation of transistor 7.2.1 Basic operation of NPN type transistor This type has been connected in opposite case to PNP type; but in this NPN type, as shown in figure below, a few holes are supplied from positive pole of electric source so that these make a small portion current of base current IB.
And electrons that come from emitter as not having been
able to join with base holes move to collector side owing to VCB of collector side so that these make collector current IC.
Ordinarily 95~98 % among emitter current IE becomes IC but remainder 2 ~5 %
becomes IB. NPN type Collector(C)
Emitter(E)
Ib [uA]
Current Ic Base(B) Current Ib Vcb
Vbe
Forward bias of NPN type transmitter: Emitter's electron most moves by collector
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Ic [mA]
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AUTOMOTRIZ ELECTRONICOS 7.2.2 Basic operation of PNP type transistor If forward voltage VBE is applied between emitter and base, electric potential barrier in between PN junction surface becomes low.
And at P type side of emitter side, many holes are being generated
because impurity material concentration has been heightened, And as for base N side, because this is very thin so that impurity material concentration becomes lower, there are only few electrons. Accordingly holes in emitter cross over the electric potential barrier and enter the base side by diffusion so as to vanish by bonding with a part of base electrons there. But because these few electrons are continuously supplied by negative “-“ pole of electric source, these make the small base current IB. If backward voltage VC B is applied between base and collector, electric potential barrier is heightened at PN junction surface so that electric current does not flow between base and collector. Holes that could not join with base electrons but come from emitter now move to collector side owing to VCB of collector side. These make collector current I C . Emitter holes are gradually supplied from positive pole so that these make emitter current Ic. Accordingly most IE becomes IC but very little portion becomes base current IB. 7.2.3 Amplification function of transistor As we have already discussed above in `Basic Operation', most electron (no less than 95 %) move to collector but only a few electrons (no more than 5 %) join with base hole.
So as electron current and
electric current direction are ordinarily defined oppositely while emitter current I E is divided into collector current I C and base current I B , the following equation holds :
I E I B IC Like this, big collector current may be deduced from small base current so as to be called electric current amplification while relationship (ratio) between I B and I C are called electric current amplification factor (h F E ). For calculation example, if I B is 1 mA and I C is 100 mA then h F E is 100. transistor that can amplify input signal by hundred times.
Namely it means
( *Electric current amplification rate of
transistor varies according to usage, sort etc . )
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AUTOMOTRIZ ELECTRONICOS
hFE
IC IB
,
100 100 1
hFE=100 C B E
Ic=100mA
Ib=1mA
Meanwhile in how to use transistor, there are three earth methods of emitter earth, base earth and collector earth among which the emitter earth method as in circuit above is most used. . Output C
Input (Ib=uA)
B E Input
Output (Ic=mA)
And generally amplification means that of alternating current component , which we shall deliberate in the following example : In circuit shown in figure here, if AC signal is applied between base and emitter, base current I B flows only when it is in forward direction (same as in diode). Whence collector current I C also appears as output while being amplified only of half wave.
Namely transistor does not operate
during negative (-) half cycle because here it is in backward direction between base and emitter.
Here let us apply DC between base and emitter.
If AC is applied onto DC, AC component is added
upon DC so as to appear like what is shown in the following figure.
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AUTOMOTRIZ ELECTRONICOS Voltage at this time is called bias voltage.
Now for the first time we can see completely amplified
output waveform. Also we may obtain the amplified AC waveform only if we remove DC component by connecting a condenser at output terminal.
Output C B Input
Input (Ib=uA)
E
Output (Ic=mA) Bias voltage
To avoid inconvenience of using two electric supplies due to bias voltage as in the depicted circuit , actual circuits use various forms adequate to purpose of each circuit by such as an electric current feedback bias, a fixed bias using a resistance, condenser etc. on the supply electricity source connected to the output terminal..
* For reference to say, there is limit area where collector current does not increase any more even though transistor base current continues to increase so as to be called the saturation region. Accordingly transistor 's amplification action is accomplished only in specific area where collector current increases in accordance with base current increase so as to be called the active area . So far we have learned electric current amplification but now let us think case of voltage amplification . According to the above explanation, we learned that collector varies proportionately with base current . Let us think this as a variable resistor to control electric current .
Then we can think the following
equivalent circuit .
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AUTOMOTRIZ ELECTRONICOS E
E R
R
Output (Eo)
Output
C
(Eo)
B Current Ic
Current Ic
E
Input current (Ib=uA)
Output Current (Ic=mA)
Output voltage (Eo=E-(Ic*R)
Under condition as above, output voltage to the base input waveform shows up reversely as may be seen in figure.
It is explained as total voltage E = voltage drop between collector and emitter (Eo) +
voltage drop due to resistance R (Ic × R).
Namely, if electric current Ic increases, voltage drop due
to resistance R also increases so that the output voltage Eo decreases.
(Output voltage Eo = E –
(Ic × R))
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AUTOMOTRIZ ELECTRONICOS Now let us learn base earth and collector earth methods along with transistor 's switching action . Base earth circuit Method of base earth is type of circuit as shown in figure to take base as earth and apply input signal to emitter.
Output E
C
B Input
