chap38 pps Automotive technology at University of Cambridge

start
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


OBJECTIVES:
After studying Chapter 38, the reader should
be able to:

•
•
•

Prepare for ASE Electrical/Electronic Systems (A6)
certification test content area “A” (General
Electrical/Electronic Systems Diagnosis).

Identify semiconductor components.
Explain precautions necessary when working around
semiconductor circuits.

Continued
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


OBJECTIVES:
After studying Chapter 38, the reader should
be able to:

•
•

•

Discuss where various electronic and semiconductor devices
are used in vehicles.
Describe how to test diodes and transistors.
List the precautions that a service technician should follow
to avoid damage to electronic components from
electrostatic discharge (ESD).

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


KEY TERMS:
anode

base • bipolar transistor • burn in
cathode • center high-mounted stoplight (CHMSL) • clamping
diode • CMOS • collector • control current
darlington pair • despiking diode • diode • doping • dual inline
pins (DIP)
electrostatic discharge (ESD) • emitter
FET • forward bias
Continued
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


KEY TERMS:
gate • germanium
heat sink • hole theory • holes

impurities • integrated circuit (IC) • junction
light-emitting diode (LED) • metal oxide varistor (MOV) •
MOSFET
negative temperature coefficient (NTC) • NPN transistor • Ntype material • OP-amps

Continued
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


KEY TERMS:
peak inverse voltage (PIV) • peak reverse voltage (PRV) •
photodiodes • photons • photoresistor • phototransistor • PNP
transistor • polarity • P-type material • PVM
rectifier bridge • reverse bias

saturation • semiconductors • silicon • silicon-controlled rectifier
(SCR) • solar cells • spike protection resistor • suppression diode
thermistor • threshold voltage • transistor • TTL
varistors • zener diode

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


Electronic components are the heart of computers.
Knowing how electronic components work helps
take the mystery out of automotive electronics.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


SEMICONDUCTORS
Semiconductors are neither conductors nor insulators. Flow of
electrical current is movement of electrons in materials having
fewer than four electrons in the atom’s outer orbit. Insulators
contain more than four electrons in their outer orbit and cannot
conduct electricity.
Semiconductors contain exactly four electrons in the outer orbit
of their atom structure and are neither good conductors nor good
insulators.
Two examples of semiconductor materials are germanium and
silicon, which have no free electrons to provide current flow.
However, both can be made to conduct current if another material
is added to provide conditions for electron movement.

Continued

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


When another material is added in very small amounts, it is called
doping. The doping elements are called impurities; and therefore,
after their addition, the germanium and silicon are no longer
considered pure elements.
The material added represents only one atom of impurity for every
100 million atoms of the pure semiconductor material. The resulting
atoms are still electrically neutral, because the number of electrons
still equals the protons of the combined materials.

These combined materials are classified into two groups depending
on the number of electrons in the bonding between the two
materials; N-type or P-type materials.

Continued
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


N-TYPE MATERIAL
N-type material is silicon or germanium doped with an element
such as phosphorus, arsenic, or antimony, each having five
electrons in its outer orbit.
These five electrons are combined with the four electrons of the
silicon or germanium to total nine electrons. There is room for

only eight electrons in the bonding between the semiconductor
material and the doping material.
This leaves extra electrons, and even though the material is still
electrically neutral, these extra electrons tend to repel other
electrons outside the material.
See Figure 38–1.
Continued
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


Figure 38–1 N-type material. Silicon (Si) doped with a material (such as phosphorus) with five
electrons in the outer orbit results in an extra free electron.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition

By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


P-TYPE MATERIAL
P-type material is produced by doping silicon or germanium with
the element boron or the element indium.
These impurities have only three electrons in their outer shell and,
when combined with the semiconductor material, result in a
material with seven electrons, one electron less than is required for
atom bonding.
This lack of one electron makes the material able to attract
electrons, even though the material still has a neutral charge. This
material tends to attract electrons to fill the holes for the missing
eighth electron in the bonding of the materials.
See Figure 38–2.

Continued
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


Figure 38–2 P-type material. Silicon (Si) doped with a material [such as boron (B)] with three
electrons in the outer orbit results in a hole capable of attracting an electron.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.

Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


HOW HOLES MOVE
Current flow is expressed as the movement of electrons from one
atom to another.
In semiconductor and electronic terms, the movement of electrons
fills the holes of the P-type material. As the holes are filled with
electrons, the unfilled holes move opposite to the flow of the
electrons.
This concept of the movement of the holes is called the hole
theory of current flow. The holes move in the direction opposite
that of electron flow.
See Figure 38–3.

Continued
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson

PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


Figure 38–3 Unlike charges attract and the current carriers (electrons and holes) move toward
the junction.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle

SaddleRiver,
River,NJ
NJ07458
07458


SUMMARY OF SEMICONDUCTORS
1. The two types of semiconductor materials are P type and N
type. N-type material contains extra electrons; P-type
material contains holes due to missing electrons. The
number of excess electrons in an N-type material must
remain constant, and the number of holes in the P-type
material must also remain constant. Because electrons are
interchangeable, movement of electrons in or out of the
material is possible to maintain a balanced material.
2. In P-type semiconductors, electrical conduction occurs
mainly as the result of holes (absence of electrons). In Ntype semiconductors, electrical conduction occurs mainly
as the result of electrons (excess of electrons).
Continued
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall

Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


3. Hole movement results from the jumping of electrons into
new positions.
4. Under the effect of a voltage applied to the semiconductor,
electrons travel toward the positive terminal and holes
move toward the negative terminal. The direction of hole
current agrees with the conventional direction of current
flow.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,

River,NJ
NJ07458
07458


DIODES
A diode is an electrical one-way check valve made by combining
a P-type material and an N-type material. The word diode means
“having two electrodes.”
The positive electrode, or electrical connection, is called the
anode, the negative electrode is the cathode.
Figure 38–4 A diode is a component with P- and N-type material together. The negative
electrode is called the cathode and the positive electrode is called the anode.

The point where the two
types of materials join
is called the junction.
Continued
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper

UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


The N-type material has one extra electron, which can flow into the
P-type material. The P type has a need for electrons to fill its holes.
If a battery were connected to the diode positive (+) to P-type
material and negative (−) to N-type material, as shown here, the
electrons that left the N-type material and flowed into the P-type
material to fill the holes would be quickly replaced by the electron
flow from the battery.
Current would flow through
the diode with low resistance.
This condition is called
forward bias.
Figure 38–5 Diode connected to a battery
with correct polarity ( to and to ). Current
flows through the diode. This condition is
called forward bias.
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

Continued
©©2008
2009Pearson
PearsonEducation,
Education,Inc.

Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


Reverse connections, and with the positive side of the battery now
connected to the N-type material, the electrons would be pulled
toward the battery, away from the junction.
Because conduction requires flow of electrons across the junction
of the N- and P-type materials and the battery connections are
actually reversed, the diode offers very high resistance to current
flow
This condition is called
reverse bias.

Figure 38–6
Diode connected with reversed polarity.
No current flows across the junction
between the P-type and N-type material.
This connection is called reverse bias.
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

Continued
©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


Diodes allow current flow only when current of the correct polarity
is connected to the circuit.
Diodes are used in alternators to control current flow in one
direction. They are also used in computer controls, air-conditioning
circuits, and many other circuits to prevent damage due to reverse
current flows that may be generated within the circuit.
Figure 38–7 Diode symbol and electrode names.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson

PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


What is the Difference Between Electricity and
Electronics?
Electronics usually means that solid-state devices are used in the
electrical circuits. Electricity as used in automotive applications usually
means electrical current flow through resistance and loads without the use
of diodes, transistors, or other electronic devices.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson

PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


ZENER DIODES
A zener diode is a specially constructed diode designed to operate
with a reverse-bias current. Zener diodes were named in 1934 for
their inventor, Clarence Melvin Zener.
A zener diode acts as any diode in that it blocks reverse-bias
current, but only up to a certain voltage. Above this voltage
(called breakdown voltage or the zener region), a zener diode will
conduct current without damage to the diode, as it is heavily
doped, and the reverse-bias voltage does not harm the material.
Zener diodes can be constructed for various breakdown voltages
and are used in many automotive and electronic applications,
especially for electronic voltage regulators. See Figure 38–8.

Continued
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,

Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


Figure 38–8 A zener diode blocks current flow until a certain voltage is reached, then it permits
current to flow.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,

River,NJ
NJ07458
07458


“Burn-In” to Be Sure
A common term heard in the electronic and computer industry is burn in.
Burn in means to operate an electronic device, such as a computer, for a
period from several hours to several days.
Most electronic devices fail in infancy, or during the first few hours of
operation. This early failure occurs if there is a manufacturing defect,
especially at the P-N junction of any semiconductor device. The junction will
usually fail after only a few operating cycles.
What does all of this information mean to the average person? When
purchasing a personal or business computer, have the computer burned
in before delivery. This step helps ensure all the circuits have survived
infancy and that the chances of chip failure are greatly reduced.
Display model sound or television equipment may be a good value,
because during its operation as a display model, it has been burned in.
The automotive service technician should be aware that if a replacement
electronic device fails shortly after installation, the problem might be a
case of early electronic failure.
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.

Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458