Semiconductor Devices II Transistors have revolutionized Electronics and our way of life. Before...
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Transcript of Semiconductor Devices II Transistors have revolutionized Electronics and our way of life. Before...
Semiconductor Devices IITransistors have revolutionized Electronics
and our way of life. Before transistors, computers were bulky, expensive, slow and highly un-reliable.
ELECTRONICS TECHNOLOGY
ELECTRONICS TECHNOLOGY
Semiconductor Devices II Transistors have revolutionized Electronics and our
way of life. Before transistors, computers were bulky, expensive, slow and highly un-reliable.
ELECTRONICS TECHNOLOGY Semiconductor Devices II
Transistors are a semiconductor device similar to diodes
ObjectiveIn this section we will learn:
1. configuration of the transistor,
2. Its usefulness
3. Its operating characteristics
ELECTRONICS TECHNOLOGY Transistors
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ELECTRONICS TECHNOLOGY Transistors
Configuration Transistors have two junctions instead of one as the
case with a junction diode.
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P N P NP P
Diode Transistor
ELECTRONICS TECHNOLOGY Transistors
Configuration Transistors Symbol is illustrated below. The identifier
is Q
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N P N
ELECTRONICS TECHNOLOGY Transistors
Configuration Transistors Symbol is illustrated below. The identifier is
Q. (Negative-Positive-Negative and Positive-Negative-Positive)
Home
Collector
Base
Emitter
Collector
Base
Emitter
NPN PNP
ELECTRONICS TECHNOLOGY Transistors
Configuration NPN Transistors have the arrow pointing outward
from the base. (Note: Never Points iN)
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Collector
Base
Emitter
NPN
Collector
Base
Emitter
PNP
ELECTRONICS TECHNOLOGY Transistors
Configuration PNP Transistors have the arrow toward the base.
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Collector
Base
Emitter
NPN
Collector
Base
Emitter
PNP
ELECTRONICS TECHNOLOGY Transistors
Configuration The emitter is heavily doped and allows for electron
flow in the semiconductor (notated by the arrow)
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Collector
Base
Emitter
NPN
ELECTRONICS TECHNOLOGY Transistors
Configuration The base is thin and is lightly doped. This configuration
allows for electron flow from Emitter to collector.
Home
NPN
Collector
Base
Emitter
ELECTRONICS TECHNOLOGY Transistors
Configuration The collector is moderately doped and is the largest
of the three. This allows for more heat loss.
Home
NPN
Collector
Base
Emitter
ELECTRONICS TECHNOLOGY Transistors
Identification The identification standard is similar to the standard
used on diodes.
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NPN
2N2222
TransistorSemiconductorPart Number
ELECTRONICS TECHNOLOGY Transistors
Pin layout The leads of a TO5 package are always configured as
shown below…
Home
NPN
E
B
C
(bottom side)
ELECTRONICS TECHNOLOGY Transistors
Pin layout The leads of a TO-92 package are always configured
as shown below…
Home
NPN
C
B
E
(bottom side)
ELECTRONICS TECHNOLOGY Transistors
Pin layout Power Transistors (type TO-3) are different. The
collector is the case
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(bottom side)
E B
Collector
(Side view)
ELECTRONICS TECHNOLOGY Transistors Biasing
Objective Understand the biasing of a transistor Define Cutoff and Saturation Define fixed, self and combinational biasing
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ELECTRONICS TECHNOLOGYTransistor Biasing
In order for a transistor to function as an amplifier, the BE junction must be forward biased.
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ELECTRONICS TECHNOLOGYTransistor Biasing
A minimum voltage VBE of .7 volts must be applied to forward bias the junction BE.
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VBE
ELECTRONICS TECHNOLOGYTransistor Biasing
In order for a transistor to work properly as an amplifier, the Collector Base (CB) junction must be reversed biased.
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ELECTRONICS TECHNOLOGYTransistor Biasing
When VBC < VBE and reverse biased, current is forced to flow as illustrated.
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N
P
N
+++
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+++
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ELECTRONICS TECHNOLOGYTransistor Biasing
Since the base material is very small compared to the collector, only a small amount of Current flows through IB.
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N
P
N
+++
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+++
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ELECTRONICS TECHNOLOGYTransistor Biasing
With this information, IC=IB+IE.
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N
P
N
+++
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+++
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ELECTRONICS TECHNOLOGYTransistor Biasing
Once the EB junction is forward biased and CB is reversed biased, Current will flow through the Transistor.
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ELECTRONICS TECHNOLOGYTransistor Biasing
Keep in mind the base is thin and lightly doped. Therefore little current flows through the base. Most of the current flows through the collector.
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