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Electronic Devices report for Environmental Engineering
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Electronic Devices
Diodes and Transistors
Classes of Materials
• Conductors – Materials with very low resistance
– Gold, Copper and Aluminum
• Insulators – Materials with very high resistance
– Dry wood and plastic
• Semiconductors – Materials with properties that fall somewhere
between conductors and insulators
Conduction
• The transfer of energy, such as heat or an electric charge, through a substance.
• Occur from the movement of either electrons or holes.
Doping – The processing of semiconductor materials for
device construction.
– Addition of impurities (donors or acceptors)
Semiconductor Material
• P-type
– Semiconductor materials having an excess of positive charge carriers
• N-type
– Materials having an excess of negative charge carriers
Diodes
Junction Diode
• Created by combining a section of P-type material with a section of N-type material.
P-type Material
N-type Material
Current flows “easily” in this
direction
Strong opposition to current flow in
this direction
Anode
Cathode
Schematic Symbol
Junction Diode
• Diode Terminal Characteristics
A
V Vs
R
Forward Bias
Breakdown Voltage
Reverse Bias
VD
ID
Threshold Voltage
Diode Circuit Models
• Ideal Diode Model
ID
VD
+
-
ID
Forward Bias
Short Circuit
Reverse Bias
Open Circuit
VR
+
-
ID
VD
Diode Circuit Models
• Constant Voltage Model
ID
VD
+
-
VD≈0.7 V + -
Forward Bias
Constant Voltage
Reverse Bias
Open Circuit
VR
+
-
ID
VD
VD≈0.7 V
Example 1
• For the circuit, determine the loop current, the voltage across the diode, and the voltage across the resistance.
I
VD
+
-
+ _
12V VR
-
+
2kΩ
Example 2
• For the circuit, determine the loop current, the voltage across the diode, and the voltage across the resistance.
I
VD
+
-
+ _
12V VR
-
+
2kΩ
Diode Rectifier Circuits
• Half-Wave Rectifier
Diode Rectifier Circuits
• Full-Wave Bridge Rectifier
Diode Clipping Circuits
Diode Clipping Circuits
Diode Clamping Circuits
Other Diode Types
• Zener Diode – It exploits the reverse breakdown voltage
• Light Emitting Diode
• Photodiode – Roughly opposite of LED
• Optocoupler – Implented with diodes consists of LED coupled with photodiode
Other Diode Types
• Schottky Diode – Special-purpose diode that reduces the
forward diffusion capacitance to a negligible
value, which permits its use into microwave
frequency range.
• Varactor Diode – It exploits the capacitance effect when diode is
reverse biased.
Transistor
Transistor
• A transistor is a semiconductor device used to amplify and switch electronic signals and electrical power.
• Three terminal active devices made from different semiconductor materials that can act as either an insulator or a conductor.
• Types: – Bipolar Junction Transistor (BJT)
– Field Effect Transistor (FET)
Bipolar Junction Transistor (BJT)
• Consists of two PN-junctions producing three connecting terminals. (base, emitter, collector)
• It is a current controlled semiconductor device.
B
E
C
B
E
C
NPN or P-type PNP or N-type
BJT Construction
Bipolar Junction Transistor (BJT)
• Basic Operation
Base Current – controlling variable
Collector Current and Emitter Current – controlled variables
• Relationship for Currents
B
E
C
BCE III
Bipolar Junction Transistor (BJT)
• BJT Operating Regions Cutoff Region
- Corresponds to reverse bias for both the base-emitter and the base-collector junctions.
Saturation Region - Corresponds to forward bias for
both base-emitter and the base-collector junctions.
Active Region - Corresponds to forward bias for the
base-emitter and reverse bias for the base-collector junctions.
Saturation Region
Active Region
Cutoff Region
BJT Configurations
• Common Base Configuration
BJT Configurations
• Common Emitter Configuration
BJT Configurations
• Common Collector Configuration
Bipolar Junction Transistor (BJT)
CBE III
B
C
I
I
E
C
I
I
Example 4
Determine the value of βdc for the idealized transistor.
IB = 100 μA
IB = 80 μA
IB = 60 μA
IB = 40 μA
IB = 20 μA
IB = 0 4 mA
20 mA
16 mA
12 mA
8 mA
IC
VCE
Field Effect Transistor (FET)
• Field effect transistor is a unipolar-transistor, which acts as a voltage-controlled current device and is a device in which current at two electrodes is controlled by the action of an electric field at another electrode.
• Field effect transistor is a device in which the current is controlled and transported by carriers of one polarity (majority) only and an electric field near the one terminal controls the current between other two.
Field Effect Transistor Family
Field Effect Transistors (FETs)
Junction Field Effect Transistors
(JFETs)
Depletion Mode
N-Channel P-Channel
Metal-oxide Semiconductor FETs (MOSFETs)
Depletion Mode
N-Channel P-Channel
Enhancement Mode
N-Channel P-Channel
BJT and FET
Junction Field Effect Transistors(JFET)
• JFET is a unipolar-transistor, which acts as a voltage controlled current device and is a device in which current at two electrodes is controlled by the action of an electric field at a p-n junction.
• Basic Construction
– Source – doped N-type material
– Drain –doped N-type material
– Gate – doped P-type material
JFET Construction
N-channel P-channel
Junction Field Effect Transistors(JFET)
• Ohmic Region – When VGS = 0 the depletion layer of the
channel is very small and the JFET acts like a voltage controlled resistor.
• Cut-Off Region
– This is also known as the pinch-off region were the Gate voltage, VGS is sufficient to cause the JFET to act as an open circuit as the channel resistance is at maximum.
• Saturation or Active Region – The JFET becomes a good conductor and is
controlled by the Gate-Source voltage, ( VGS ) while the Drain-Source voltage, ( VDS ) has little or no effect.
• Breakdown Region – The voltage between the Drain and the
Source, ( VDS ) is high enough to causes the JFET’s resistive channel to break down and pass uncontrolled maximum current.
Metal-Oxide Semiconductor Field effect Transistor (MOSFET)
• MOSFET is a voltage controlled majority carrier device. Movement of majority carriers in a MOSFET is controlled by the voltage applied on the control electrode (called gate) which is insulated by a thin metal oxide layer from the bulk semiconductor body.
MOSFET Configuration
•
N-type P-type
