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CHAPTER. Basic Electronics. 6. Instructor Name: (Your Name ). Learning Objectives. List the various types of resistors Determine whether a diode is forward biased or reverse biased in a circuit Test a diode with a DMM Explain the function of a zener diode - PowerPoint PPT Presentation
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Copyright © 2014 Delmar, Cengage Learning
Basic Electronics
Instructor Name: (Your Name)
6CHAPTER
Copyright © 2014 Delmar, Cengage Learning
Learning Objectives• List the various types of resistors• Determine whether a diode is forward biased
or reverse biased in a circuit• Test a diode with a DMM• Explain the function of a zener diode• Describe the operation of a bipolar transistor• Explain the difference between a transistor
being used as an amplifier and a transistor being used as a relay or a switch
Copyright © 2014 Delmar, Cengage Learning
Learning Objectives (continued)
• Describe the operation of a field effect transistor (FET)
• Discuss the concept of a high side driver and a low side driver
Copyright © 2014 Delmar, Cengage Learning
Resistors• Limit the current flow through a circuit• Divide voltage• Give off heat• Two main types of resistors; fixed and
variable
Copyright © 2014 Delmar, Cengage Learning
Fixed Resistors and Color Code
Figure 6-1 Fixed-value resistors: physical size of resistor increases as wattage rating of resistor increases. Figure 6-2 Resistor color code.
Copyright © 2014 Delmar, Cengage Learning
Stepped Value Variable Resistor
Figure 6-3 Stepped-value resistor network.
Copyright © 2014 Delmar, Cengage Learning
Infinitely Variable Resistor
Figure 6-4 Infinitely variable resistor.
Copyright © 2014 Delmar, Cengage Learning
Potentiometer
Figure 6-7 Potentiometer.
Copyright © 2014 Delmar, Cengage Learning
Semiconductors• A material that is neither a good nor a poor
conductor• Silicon is the most common used in electronics• Semiconductors usually have a negative
temperature coefficient (NTC)• Pure silicon has four valence electrons• Impurities added to silicone is a process called
doping• Doping with a material that has excessive
electrons creates an N-type junction• Doping with a material that has excessive holes
creates a P-type junction
Copyright © 2014 Delmar, Cengage Learning
N-Type Semiconductor Doped With Arsenic
Figure 6-9 N-Type semiconductor doped with arsenic (As).
Copyright © 2014 Delmar, Cengage Learning
P-Type Semiconductor Doped With Boron
Figure 6-10 P-Type semiconductor doped with boron (B).
Copyright © 2014 Delmar, Cengage Learning
Diodes• Two terminal semiconductor that acts as a one
way check valve to current flow• The schematic symbol of a diode shows the
direction of current flow through the device• If a diode is inserted in a circuit so that it
allows current flow it is forward biased• If a diode is inserted in a circuit so that is does
not allow current flow it is reversed biased• The positive terminal of a diode is the anode• The negative terminal of a diode the cathode
Copyright © 2014 Delmar, Cengage Learning
Diode and Schematic Symbol
Figure 6-15 Stripe indicates cathode end of diode. Figure 6-12 Diode voltage.
Copyright © 2014 Delmar, Cengage Learning
Diodes (continued)
• Diodes will not permit current flow in the forward bias direction until 0.7V is dropped across the diode
• A diode will always drop approximately 0.7V regardless of the current or voltage in the circuit
• Diodes have a rated limit to reverse bias voltage called the inverse voltage rating
• If the inverse voltage rating is exceeded the diode will be destroyed
Copyright © 2014 Delmar, Cengage Learning
Diode Testing With a DMM
Figure 6-19 Diode testing using DMM.
Copyright © 2014 Delmar, Cengage Learning
Light-Emitting Diodes
Figure 6-21 Schematic symbol for LED.
Copyright © 2014 Delmar, Cengage Learning
Zener Diode
• In the forward biased direction zener diodes act like a regular diode and allow current flow
• A zener diode has a rating referred to the zener voltage
• Once the zener voltage is reached in the reverse bias direction the zener will switch on and conduct current in the reversed bias direction
Copyright © 2014 Delmar, Cengage Learning
Bipolar Transistors
• Bipolar transistors are made up of P-type and N-type junctions
• There are two major types of bipolar transistors PNP and NPN
• A PNP type is like a sandwich of N-type material between two slices of P-type material
• An NPN type is like a sandwich of P-type material between two slices of N-type material
Copyright © 2014 Delmar, Cengage Learning
NPN Bipolar Transistor
Figure 6-26 NPN bipolar transistor.
Copyright © 2014 Delmar, Cengage Learning
Bipolar Transistors (continued)
• The P-type layer of an NPN transistor is the base
• One of the N-type layers is called the emitter• The other N-type layer is called the collector• The emitter, collector, and base are labeled E,
C, and B• Transistors amplify low level signals to a
higher level signal• Transistors act as switches similar to a relay
Copyright © 2014 Delmar, Cengage Learning
Bipolar Transistors (continued)
• The collector of a bipolar transistor is connected to the positive terminal of the supply voltage
• The base of a bipolar transistor is connected to the small signal that will be amplified
• The emitter of a bipolar transistor is connected to the load device and the load is connected to the negative terminal of the supply voltage
Copyright © 2014 Delmar, Cengage Learning
Transistor Amplifying the Base Current
Figure 6-28 Transistor amplifying the base current.
Copyright © 2014 Delmar, Cengage Learning
NPN Transistor Used As a Switch
Figure 6-29 NPN transistor used as a switch.
Copyright © 2014 Delmar, Cengage Learning
Transistors Connected as a Darlington Pair
Figure 6-30 Darlington pair permits a very small current to control a very large current.
Copyright © 2014 Delmar, Cengage Learning
Field Effect Transistors (FET)• FET’s are controlled by voltage not current• The drain of an FET corresponds to the
collector of a bipolar transistor• The gate of an FET corresponds to the base
of a bipolar transistor• The source of an FET corresponds to the
emitter of a bipolar transistor• The voltage difference between the gate and
the source voltage controls the resistance between the drain and the source
Copyright © 2014 Delmar, Cengage Learning
N-Channel JFET Schematic Symbol
Figure 6-31 N-channel JFET schematic symbol.
Copyright © 2014 Delmar, Cengage Learning
P-Channel JFET
Figure 6-32 P-channel JFET is similar to a normally closed relay.
Copyright © 2014 Delmar, Cengage Learning
Metal Oxide Semiconductor FET
Figure 6-33 Enhancement-mode MOSFET symbols.
Copyright © 2014 Delmar, Cengage Learning
Drivers
• Drivers are transistors used to switch high-current devices
• When the transistor is providing a path to ground it is described as a low side driver
• When a device is providing a path to ground it is said to be sinking
• When the transistor is providing a path for positive voltage it is describes as a high side device
• When a device is providing power it is said to be sourcing
Copyright © 2014 Delmar, Cengage Learning
Low Side Driver Sinks Current to Ground
Figure 6-34 Low side driver sinks current to ground.
Copyright © 2014 Delmar, Cengage Learning
High Side Driver Sources Current to the Load
Figure 6-35 High side driver sources current to the load.
Copyright © 2014 Delmar, Cengage Learning
Tech Tip
A device controlled by a low side driver located inside an electronic control module will typically be connected to a positive voltage at one terminal and the electronic control module on the other. A device controlled by a high side driver will typically be connected to ground at one terminal and the electronic control module at the other terminal.
Copyright © 2014 Delmar, Cengage Learning
Voltage Dropped Across Transistor Collector to Emitter
Figure 6-36 Voltage dropped across transistor collector to emitter indicates transistor is acting as an amplifier.
Copyright © 2014 Delmar, Cengage Learning
Transistor Acting as a Switch
Figure 6-37 Transistor saturated; increasing base current will not result in any additional collector-emitter current; transistor is acting as a switch in ON position.
Copyright © 2014 Delmar, Cengage Learning
Summary• Resistors are used for three main purposes;
limit current flow, divide voltage, and give off heat. Resistors may be fixed or variable value.
• A rheostat is a two terminal variable resistor. A rheostat is often used to control the amount of current flow in a circuit. A wiper moves over a resistive track, causing a change in the amount of resistance between two terminals.
• A potentiometer is a three terminal variable resistor. A potentiometer is typically used to divide voltage.
Copyright © 2014 Delmar, Cengage Learning
Summary (continued)• A diode is a two terminal device that acts as a
one way check valve for current flow. When current is flowing through the diode, the diode is said to be forward biased. When the diode is blocking the flow of current, the diode is said to be reversed biased.
• Diodes and many other electronic devices are made of silicon. Silicon mixed with impurities can form N-type and P-type semiconductor materials. Placing these two types of silicon next to each other causes a junction to form. This PN junction is the basis of many electronic components.
Copyright © 2014 Delmar, Cengage Learning
Summary (continued)• The positive end of a diode is known as the
anode; the negative end of a diode is know as the cathode. A stripe around the girth of a diode signifies the cathode end of the diode.
• Diodes can be tested outside a circuit using a DMM or an analog ohmmeter. The diode should have a very high resistance when reverse biased by the ohmmeter, and a very low resistance when forward biased by the ohmmeter.
Copyright © 2014 Delmar, Cengage Learning
Summary (continued)
• A light emitting diode (LED) is a special diode that gives off visible light when forward biased. An LED always requires some sort of means of limiting current flow through the LED, unlike standard light bulbs.
• A zener diode is a special diode that acts like a standard rectifier diode in the forward biased direction. In the reverse biased direction, the zener diode will permit current flow after the zener voltage is reached.
Copyright © 2014 Delmar, Cengage Learning
Summary (continued)
• A transistor is a device that amplifies a small signal into a large signal. A transistor can be used as an amplifier in devices such as radios. A transistor can also be used as a relay.
• Bipolar transistors are three terminal devices and contain two PN-type material junctions. The three terminal are identified as the base, collector, and emitter. Bipolar transistors are current controlled devices. Bipolar transistors can be NPN or PNP type.
Copyright © 2014 Delmar, Cengage Learning
Summary (continued)• Field effect transistors (FET) are three
terminal devices. The three terminal are identified as the source, gate, and drain. FETs are voltage controlled devices.
• Transistors that are used as relays may be called drivers. Drivers that provide a path to ground for a device when switched on are known as low side devices. A low side driver is said to sink current. Drivers that supply a positive voltage when switched on are called high side drivers. A high side driver is said to source current.