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OBJECTIVES
After studying Chapter 14, the reader should be able to:
1. Prepare for ASE Electrical/Electronic Systems (A6)
certification test content area “A” (General
Electrical/Electronic Systems Diagnosis).
2. Identify semiconductor components.
3. Explain precautions necessary when working around
semiconductor circuits.
4. Discuss where various electronic and semiconductor
devices are used in vehicles.
5. Describe how to test diodes and transistors.
6. List the precautions that a service technician should follow
to avoid damage to electronic components from ESD.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SEMICONDUCTORS
• Semiconductors are materials that contain exactly
four electrons in the outer orbit of their atom
structure and are, therefore, neither good
conductors nor good insulators.
• When another material is added to a semiconductor
material in very small amounts, it is called doping.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
N-TYPE MATERIAL
• N-type material is silicon
or germanium that is doped
with an element such as
phosphorus, arsenic, or
antimony, each having five
electrons in its outer orbit.
FIGURE 14-1 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.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 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.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
P-TYPE MATERIAL
FIGURE 14-2 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.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 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.
• Therefore, as the holes are filled with electrons, the unfilled
holes move opposite to the flow of the electrons.
• This concept of holes movement is called the hole theory of
current flow.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
HOW HOLES MOVE
• The holes move in the direction opposite that of electron
flow.
FIGURE 14-3 Unlike charges attract and the current
carriers (electrons and holes) move toward the
junction.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SUMMARY OF SEMICONDUCTORS
• The following is a summary of semiconductor fundamentals.
– The two types of semiconductor materials are P type and N type. Ntype material contains extra electrons; P-type material contains holes
due to missing electrons.
– In P-type semiconductors, electrical conduction occurs mainly as the
result of holes (absence of electrons).
– Hole movement results from the jumping of electrons into new
positions.
– Under the effect of a voltage applied to the semiconductor, electrons
travel toward the positive terminal and holes move toward the
negative terminal.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 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.”
• Electrodes are electrical connections:
– The positive electrode is called the anode; the negative
electrode is called the cathode.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
DIODES
FIGURE 14-4 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.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
DIODES
FIGURE 14-5 Diode connected to a battery with correct
polarity (+ to + and - to -). Current flows through the
diode. This condition is called forward bias.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
DIODES
FIGURE 14-6 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.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
FIGURE 14-7 Diode symbol and
electrode names.
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ZENER DIODES
• A zener diode is a specially constructed diode
designed to operate with a reverse-bias current.
• Zener diodes can be constructed for various
breakdown voltages and can be used in a variety of
automotive and electronic applications, especially
for electronic voltage regulators.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ZENER DIODES
FIGURE 14-8 A zener diode blocks current flow until a certain
voltage is reached, then it permits current to flow.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CLAMPING DIODES
• Diodes can be used as a high-voltage clamping device when
the power (+) is connected to the cathode (-) of the diode.
• A diode connected across the terminals of a coil to control
voltage spikes is called a clamping diode.
FIGURE 14-9 (a) Notice that when the coil is being energized, the diode is reverse biased and
the current is blocked from passing through the diode. The current flows through the coil
in the normal direction. (b) When the switch is opened, the magnetic field surrounding the coil
collapses, producing a high-voltage surge in the reverse polarity of the applied voltage. This
voltage surge forward biases the diode, and the surge is dissipated harmlessly back through
the windings of the coil.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CLAMPING DIODES
• Diodes were first used on
AC compressor clutch coils
at the same time electronic
devices were first used.
FIGURE 14-10 Spike protection diodes are
commonly used in computer-controlled circuits
to prevent damaging high-voltage surges that
occur anytime current flowing through a coil is
stopped.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ZENER DIODE DESPIKING PROTECTION
• Zener diodes can also be
used to control high-voltage
spikes and keep them from
damaging delicate
electronic circuits.
FIGURE 14-11 A zener diode is commonly used inside automotive
computers to protect delicate electronic circuits from high-voltage spike. A
35 volt zener diode will conduct any voltage spike resulting from the
discharge of a coil safely to ground through a current-limiting resistor in
series with the zener diode.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
DESPIKING PROTECTIVE RESISTORS
• All coils must use some
protection against highvoltage spikes that occur
when the voltage is
removed from any coil.
• Instead of a diode installed
in parallel with the coil
windings, a resistor can be
used and is called a spike
protection resistor.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
FIGURE 14-12 A despiking resistor is used in
many automotive applications to help prevent
harmful high-voltage surges from being created
when the magnetic field surrounding a coil
collapses when the coil circuit is
opened.
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DESPIKING PROTECTIVE RESISTORS
• Resistors are often preferred for two reasons.
– Coils will usually fail when shorted rather than open, as
this shorted condition results in greater current flow in the
circuit.
– The protective diode can also fail, and diodes usually fail
shorted before they blow open.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
DIODE RATINGS
• Most diodes are rated according to their maximum
current flow in the forward-bias direction and their
resistance to high voltage in the reverse-bias
direction.
• This rating of resistance to reverse-bias voltage is
called the peak inverse voltage (PIV) rating, or the
peak reverse voltage (PRV) rating.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
DIODE RATINGS
• Typical 1 ampere diodes use a code that indicates
the PIV rating.
• For example:
–
–
–
–
–
1N 4001-50 V PIV
1N 4002-100 V PIV
1N 4003-200 V PIV
1N 4004-400 V PIV
1N 4005-600 V PIV
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
LIGHT-EMITTING DIODES
• Light-emitting diodes (LEDs) radiate light when current flows
through the diode in the forward-bias direction.
FIGURE 14-13 Typical LED. The longer of the two electrodes of an LED is the anode.
Some LEDs use equal-length electrodes, and determination of which electrode to connect
to which polarity must be made using an ohmmeter or the “diode check” position of a
digital meter.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
PHOTODIODES
• All P-N junctions emit
energy, mostly in the form
of heat or light such as with
an LED.
• Photodiodes are specially
constructed to respond to
various wavelengths of light
with a “window” built into
the housing.
FIGURE 14-14 Typical photodiodes.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
PHOTODIODES
FIGURE 14-15 Symbol for a photodiode. The arrows represent lights
striking the P-N junction of the photodiode.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
PHOTORESISTORS
• A photoresistor is a semiconductor material
(usually cadmium sulfide) that changes resistance
with the presence or absence of light.
– Dark = high resistance
– Light = low resistance
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
PHOTORESISTORS
FIGURE 14-16 Either symbol may be used to represent a
photoresistor.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
VARISTORS
• Varistors are resistors whose resistance depends
on the level of voltage applied.
• A varistor, or metal oxide varistor (MOV), operates
similarly to two back-to-back zener diodes.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SILICON-CONTROLLED RECTIFIERS
• A silicon-controlled rectifier (SCR) is commonly used in the
electronic circuits of various automotive applications.
• An SCR is a semiconductor device that looks like two diodes
connected end to end.
FIGURE 14-17 Symbol and terminal identification of an SCR.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SILICON-CONTROLLED RECTIFIERS
FIGURE 14-18 Wiring diagram for a CHMSL.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
THERMISTORS
• A thermistor is a semiconductor material such as silicon
that has been doped to provide a given resistance.
FIGURE 14-19 Symbols used to represent a thermistor.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
RECTIFIER BRIDGES
• A rectifier bridge is a group of diodes that is used
to change alternating current into direct current.
• A rectifier bridge is used in alternators to rectify the
alternating current produced in the stator (stationary
windings) of the generator (alternator).
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
RECTIFIER BRIDGES
FIGURE 14-20 This rectifier bridge contains six
diodes; three on each side and mounted in an
aluminum-finned unit to help keep the diode cool
during generator (alternator) operation.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
TRANSISTORS
• A transistor is a semiconductor device that can perform the
following electrical functions.
– Act as an electrical switch in a circuit.
– Act as an amplifier of current in a circuit.
– Regulate the current in a circuit.
FIGURE 14-21 Bipolar transistors use P- and N-type materials to form
the three parts of a transistor. The P- and N-type materials can be arranged
either as a PNP transistor or an NPN transistor. The difference is in how the transistor
is turned on or off. Positive voltage to the base turns on an NPN transistor
whereas a lower or negative voltage is necessary to turn on a PNP transistor.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
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TRANSISTORS
• The center section of a transistor is called the base; it
controls current flow through the transistor
FIGURE 14-22 The three parts of a transistor are the
emitter (E), the base (B), and the collector (C).
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
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TRANSISTORS
FIGURE 14-23 The symbols and parts of a typical bipolar transistor.
Notice that the arrow is always on the emitter and points toward the Ntype material.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
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HOW A TRANSISTOR WORKS
• A transistor is similar to two back-to-back diodes
that can conduct current in only one direction.
• A transistor will allow current flow if the electrical
conditions allow it to switch on, in a manner similar
to the working of an electromagnetic relay.
Diagnosis and Troubleshooting of Automotive Electrical,
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By James D. Halderman
© 2010 Pearson Higher Education, Inc.
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HOW A TRANSISTOR WORKS
FIGURE 14-24 Basic transistor operation. A small current flowing
through the base and emitter of the transistor turns on the transistor and
permits a higher-amperage current to flow from the collector and the
emitter.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
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HOW A TRANSISTOR AMPLIFIES
• A transistor can amplify a signal if the signal is
strong enough to trigger the base of a transistor on
and off.
• The resulting on–off current flow through the
transistor can be connected to a higher-powered
electrical circuit.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
FIELD-EFFECT TRANSISTORS
• Field-effect transistors (FETs) have been used in
most automotive applications since the mid-1980s.
• They use less electrical current and rely mostly on
the strength of a small voltage signal to control the
output.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
FIELD-EFFECT TRANSISTORS
FIGURE 14-25 The three terminals of a field-effect transistor (FET)
are called the source, gate, and drain.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
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DARLINGTON PAIRS
• A Darlington pair consists of two transistors wired together.
• This arrangement permits a very small current flow to control
a large current flow.
FIGURE 14-26 A Darlington pair consists of two transistors wired
together, allowing a very small current to control a large current flow.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
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TRANSISTOR GAIN
• A transistor can do more than switch on and off
when the base is triggered. Most transistors can
also amplify.
• In an NPN transistor, for example, if the base
voltage is higher than emitter voltage (by about 0.6
volt or more), current will flow from collector to
emitter.
Diagnosis and Troubleshooting of Automotive Electrical,
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By James D. Halderman
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SOLID-STATE, INTEGRATEDCIRCUIT, AND DUALINLINE PACKAGE COMPONENTS
• Solid-state components are used in many electronic
semiconductors and/or circuits.
• They are called “solid state” because they have no
moving parts, just higher or lower voltage levels
within the circuit.
Diagnosis and Troubleshooting of Automotive Electrical,
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By James D. Halderman
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SOLID-STATE, INTEGRATEDCIRCUIT, AND DUALINLINE PACKAGE COMPONENTS
• Newer-style electronic devices use the same
components, but they are now combined
(integrated) into one group of circuits, and are thus
called an integrated circuit (IC).
• Integrated circuits are usually encased in a plastic
housing called a CHIP with two rows of inline pins;
this arrangement is called the dual inline pins
(DIP) chips.
Diagnosis and Troubleshooting of Automotive Electrical,
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By James D. Halderman
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SOLID-STATE, INTEGRATEDCIRCUIT, AND DUALINLINE PACKAGE COMPONENTS
FIGURE 14-27 Typical dual inline package chip with identifying
information explained.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
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HEAT SINK
• Heat sink is a term used to describe any area around an
electronic component that, because of its shape or design,
can conduct damaging heat away from electronic parts.
• Examples of heat sinks include the following:
– Ribbed electronic ignition control units
– Cooling slits and cooling fan attached to a generator (alternator)
– Special heat-conducting grease under the electronic ignition module
in all General Motors HEI systems
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
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PHOTOTRANSISTORS
• Similar in operation to a photodiode, a phototransistor uses
light energy to turn on the base of a transistor.
• Phototransistors are frequently used in steering wheel
controls.
FIGURE 14-28 Symbols for a phototransistor: (a) shows a line for
the base; (b) does not show a line for the base.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
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SOLAR CELLS
• Solar cells are another type of semiconductor
device where light energy is used to produce a
small current flow by dislodging electrons within the
structure.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
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HOW TO TEST DIODES AND TRANSISTORS
• Diodes and transistors can
be tested with an
ohmmeter.
FIGURE 14-29 To check a diode, select “diode
check” on a digital multimeter. The display will
indicate the voltage drop (difference) between the
meter leads. The meter itself applies a low-voltage
signal (usually about 3 volts) and displays the
difference on the display. (a) When the diode is
forward biased, the meter should display a voltage
between 0.500 and 0.700 V (500 mV to 700 mV). (b)
When the meter leads are reversed, the meter
should read OL (over limit) because the diode is
reverse biased and blocking current flow.
Diagnosis and Troubleshooting of Automotive Electrical,
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By James D. Halderman
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HOW TO TEST DIODES AND TRANSISTORS
Diodes
• A good diode should give an over limit (OL) reading
with the test leads attached to each lead of the
diode in one way, and a voltage reading of 0.400 to
0.600 V when the leads are reversed.
Diagnosis and Troubleshooting of Automotive Electrical,
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By James D. Halderman
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HOW TO TEST DIODES AND TRANSISTORS
Transistors
• A good transistor should show continuity (between
0.400 and 0.600 V) between the emitter (E ) and the
base (B) and between the base (B ) and the
collector (C) with a meter connected one way, and
OL when the meter test leads are reversed.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
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HOW TO TEST DIODES AND TRANSISTORS
Transistors
FIGURE 14-30 PNP and NPN transistors
look alike if you are not familiar with small,
detailed manufacturers’ markings. The best
way to determine which type of transistor you
have is to test it.
Diagnosis and Troubleshooting of Automotive Electrical,
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By James D. Halderman
FIGURE 14-31 If the red (positive) lead of
the ohmmeter (or a multimeter set to diode
check) is touched to the center and the
black (negative lead) touched to either end
of the electrode, the meter should forward
bias the P-N junction and indicate on the
meter as low resistance. If the meter reads
high resistance, reverse the meter leads,
putting the black on the center lead and the
red on either end lead. If the meter
indicates low resistance, the transistor is a
good PNP type. Check all P-N junctions in
the same way.
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TRANSISTOR GATES
• A gate is an electronic
circuit whose output
depends on the location
and voltage of two inputs.
FIGURE 14-32 Typical transistor AND-gate
circuit. Notice that both transistors must be
turned on before there will be voltage present
at the point labeled “signal out.”
Diagnosis and Troubleshooting of Automotive Electrical,
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LOGIC HIGHS AND LOWS
• All computer circuits and most electronic circuits
(such as gates) use various combinations of high
and low voltages.
• High voltages are typically those above 5 volts, and
low is generally considered zero (ground).
Diagnosis and Troubleshooting of Automotive Electrical,
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TRANSISTOR–TRANSISTOR LOGIC
• Transistor–transistor logic (TTL) uses 5 volts as a
reference, with high being slightly less than 5 volts
and low being slightly above 0 volt.
• TTL chips consume more electrical power, and
therefore generate more heat, than newer ICs using
complementary metal oxide semiconductor
(CMOS) technology.
Diagnosis and Troubleshooting of Automotive Electrical,
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OPERATIONAL AMPLIFIERS
• Operational amplifiers (OP-amps) are frequently referred
to simply as op-amps.
• Op-amps are used in circuits to control and amplify digital
signals.
FIGURE 14-33 Symbol for an operational amplifier (op-amp).
Diagnosis and Troubleshooting of Automotive Electrical,
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By James D. Halderman
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POLARITY
• Polarity, in electrical terms, means positive (+) or
negative (-) electrical potential of a wire,
component, or circuit.
• Polarity usually indicates which terminal of a battery
(or other power supply) should be connected to
which terminal of a component.
Diagnosis and Troubleshooting of Automotive Electrical,
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By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
POLARITY
FIGURE 14-34 Polarity is marked on this capacitor with arrows.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELECTRONIC COMPONENT FAILURE CAUSES
• Electronic components such as electronic ignition modules,
electronic voltage regulators, onboard computers, and any
other electronic circuit are generally very reliable; however,
failure can occur.
• Following are frequent causes of premature failure.
–
–
–
–
Poor Connections
Heat
Voltage Spikes
Excessive Current
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELECTRONIC COMPONENT FAILURE CAUSES
FIGURE 14-35 The length of on-time is called the pulse width.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
BLINKING LED THEFT DETERRENT
• A blinking (flashing) LED consumes only about 5
milliamperes (5/1,000 of 1 ampere or 0.005 A).
• Most alarm systems use a blinking red LED to
indicate that the system is armed.
• A fake alarm indicator is easy to make and install.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
BLINKING LED THEFT DETERRENT
FIGURE 14-36 Schematic for a blinking LED theft deterrent.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CONVERTERS AND INVERTERS
Converters
• DC to DC converters (usually written DC-DC
converter) are electronic devices used to transform
DC voltage from one level of DC voltage to another
higher or lower level.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CONVERTERS AND INVERTERS
Converters
FIGURE 14-37 A DC to DC converter is built into most powertrain control modules (PCM)
and is used to supply the five volt reference called V-ref to many sensors used to control
the internal combustion engine.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CONVERTERS AND INVERTERS
Converters
FIGURE 14-38 This DC-DC converter is designed to convert 42 volts to 14 volts to provide
14V power to accessories on a hybrid/electric vehicle operating with a 42 volt electrical
system.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CONVERTERS AND INVERTERS
DC-DC Converter Circuit Testing
• Usually a DC control voltage is used which is
supplied by a digital logic circuit to shift the voltage
level to control the converter.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CONVERTERS AND INVERTERS
Inverters
• An inverter is an electronic circuit that changes
direct current (DC) into alternating current (AC).
• An inverter converts DC power to AC power at the
required frequency and amplitude.
• The inverter consists of three half-bridge units and
the output voltage is mostly created by a pulse
width modulation (PWM) technique.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CONVERTERS AND INVERTERS
Inverters
FIGURE 14-39 A typical circuit for an inverter designed to change DC current from a
battery to AC current for use by the electric motors used in a hybrid electric vehicle.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CONVERTERS AND INVERTERS
Inverters
FIGURE 14-40 The switching (pulsing) MOSFETs create a
waveform called a modified sine wave (solid lines) compared to
a true sine wave (dotted lines).
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELECTROSTATIC DISCHARGE
• Electrostatic discharge (ESD) is created when
static charges build up on the human body when
movement occurs.
• The friction of the clothing and the movement of
shoes against carpet or vinyl floors cause a high
voltage to build.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELECTROSTATIC DISCHARGE
• To help prevent damage to components, follow
these easy steps.
– Keep the replacement electronic component in the
protective wrapping until just before installation.
– Before handling any electronic component, ground
yourself to a good conductor to drain away any static
charge.
– Do not touch the terminals of electronic components.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SUMMARY
1.
2.
3.
3.
4.
5.
Semiconductors are constructed by doping semiconductor
materials such as silicon.
N-type and P-type materials can be combined to form
diodes, transistors, SCRs, and computer chips.
Diodes can be used to direct and control current flow in
circuits and to provide despiking protection.
Transistors are electronic relays that can also amplify.
All semiconductors can be damaged if subjected to
excessive voltage, current, or heat.
Never touch the terminals of a computer or electronic
device; static electricity can damage electronic
components.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
REVIEW QUESTIONS
1. Explain the difference between P-type material
and N-type material.
2. Describe how a diode can be used to suppress
high-voltage surges in automotive components or
circuits containing a coil.
3. Explain how a transistor works.
4. List the precautions to which all service
technicians should adhere in order to avoid
damage to electronic and computer circuits.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
1. A semiconductor is a material _____.
a) With fewer than four electrons in the outer orbit of its
atoms
b) With more than four electrons in the outer orbit of its
atoms
c) With exactly four electrons in the outer orbit of its atoms
d) Determined by other factors besides the number of
electrons
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
1. A semiconductor is a material _____.
a) With fewer than four electrons in the outer orbit of its
atoms
b) With more than four electrons in the outer orbit of its
atoms
c) With exactly four electrons in the outer orbit of its atoms
d) Determined by other factors besides the number of
electrons
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
2. The arrow in a symbol for a semiconductor device
_____.
a)
b)
c)
d)
Points toward the negative
Points away from the negative
Is attached to the emitter
Both a and c are correct
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
2. The arrow in a symbol for a semiconductor device
_____.
a)
b)
c)
d)
Points toward the negative
Points away from the negative
Is attached to the emitter
Both a and c are correct
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
3. To forward bias a silicon diode, _____.
a) The voltage at the anode must exceed the voltage at
the cathode by 0.5 to 0.7 volt
b) The voltage at the cathode must exceed the voltage at
the anode by 0.3 to 0.5 volt
c) The voltage at the anode must exceed the voltage at
the cathode by 0.3 to 0.5 volt
d) The anode must be connected to a resistor (300 to 500
ohms) and 12 volts, with the cathode also connected to
12 volts
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
3. To forward bias a silicon diode, _____.
a) The voltage at the anode must exceed the voltage at
the cathode by 0.5 to 0.7 volt
b) The voltage at the cathode must exceed the voltage at
the anode by 0.3 to 0.5 volt
c) The voltage at the anode must exceed the voltage at
the cathode by 0.3 to 0.5 volt
d) The anode must be connected to a resistor (300 to 500
ohms) and 12 volts, with the cathode also connected to
12 volts
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
4. A transistor is controlled by the polarity and
current at _____.
a)
b)
c)
d)
The collector
The emitter
The base
Both a and b
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
4. A transistor is controlled by the polarity and
current at _____.
a)
b)
c)
d)
The collector
The emitter
The base
Both a and b
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
5. A transistor can _____.
a)
b)
c)
d)
Switch on and off
Amplify
Throttle
Do all of the above
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
5. A transistor can _____.
a)
b)
c)
d)
Switch on and off
Amplify
Throttle
Do all of the above
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
6. Clamping diodes _____.
a) Are connected into a circuit with the positive () voltage
source to the cathode and the negative () voltage to the
anode
b) Are also called despiking diodes
c) Can suppress transient voltages
d) Are all of the above
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
6. Clamping diodes _____.
a) Are connected into a circuit with the positive () voltage
source to the cathode and the negative () voltage to the
anode
b) Are also called despiking diodes
c) Can suppress transient voltages
d) Are all of the above
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
7. A zener diode is normally used for voltage
regulation. A zener diode, however, can also be
used for high-voltage spike protection if connected
_____.
a) Positive to anode, negative to cathode
b) Positive to cathode, ground to anode
c) Negative to anode, cathode to a resistor then to a
lowervoltage terminal
d) Both a and c
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
7. A zener diode is normally used for voltage
regulation. A zener diode, however, can also be
used for high-voltage spike protection if connected
_____.
a) Positive to anode, negative to cathode
b) Positive to cathode, ground to anode
c) Negative to anode, cathode to a resistor then to a
lowervoltage terminal
d) Both a and c
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
8. The forward-bias voltage required for an LED is
_____.
a)
b)
c)
d)
0.3 to 0.5 volt
0.5 to 0.7 volt
1.5 to 2.2 volts
4.5 to 5.1 volts
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
8. The forward-bias voltage required for an LED is
_____.
a)
b)
c)
d)
0.3 to 0.5 volt
0.5 to 0.7 volt
1.5 to 2.2 volts
4.5 to 5.1 volts
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
9. A good NPN transistor should test low resistance
(low-voltage drop) between the _____ and
_____, and high resistance (over limit voltage
drop) between the _____ and _____.
a)
b)
c)
d)
Base; emitter; emitter; collector
Emitter; collector; gate; trigger
Trigger; base; collector; gate
Collector; base; emitter; base
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
9. A good NPN transistor should test low resistance
(low-voltage drop) between the _____ and
_____, and high resistance (over limit voltage
drop) between the _____ and _____.
a)
b)
c)
d)
Base; emitter; emitter; collector
Emitter; collector; gate; trigger
Trigger; base; collector; gate
Collector; base; emitter; base
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
10. Another name for a computer ground is _____.
a)
b)
c)
d)
Logic low
Zero
Reference low
All of the above
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
10. Another name for a computer ground is _____.
a)
b)
c)
d)
Logic low
Zero
Reference low
All of the above
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
END
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458