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8/13/2019 13-Chapter 13 - Transistors
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Chapter 13
Transistors
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Introduction
Transistors are three terminal devices thatreplaced vacuum tubes.
They are solid state devices that are used for AmplificationSwitchingDetecting Light
The three terminals are the Emitter, Base, Collector (BJT)Source, Gate, Drain (FET)
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The BJT
Bipolar Junction Transistors are made withn-type and p-type semiconductors.
There are two types: npn and pnp.
Circuit Symbols
Transistor Analogy
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Diodes
p-type n-type
Circuit Symbol
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A Bipolar Transistor essentially consists of a pair of PN JunctionDiodes that are joined back-to-back.
This forms a sort of a sandwich where one kind of semiconductor is placed in between two others.
There are therefore two kinds of Bipolar sandwich, the NPN andPNP varieties.
The three layers of thesandwich are conventionallycalled the Collector, Base,and Emitter.
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Some of the basic properties exhibited bya Bipolar Transistor are immediatelyrecognizable as being diode-like.
However, when the 'filling' of the
sandwich is fairly thin some interestingeffects become possible that allow us touse the Transistor as an amplifier or aswitch.
To see how the Bipolar Transistor workswe can concentrate on the NPN variety.
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Transistor Equations
Alpha Factor
Current Gain
Kirchhoffs Current Rule
E
C
i
i
B
C
i
i
BCE iii
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What are the primaryuses of transistors?
1. Switching (Logic Gates)
2. Amplification (Op-Amps)
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Logic Gates
NOTANDOR
NAND
NORXORXNOR
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H-bridge circuit for controlling motors.http://www.cpg1.freeserve.co.uk/servos/servos.htm
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Chapter 14
OperationalAmplifiers
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741 Operational Amplifier
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Introduction
Operational Amplifiers areintegrated circuits (ICs) thathave a number of advantagesover the standalone transistors.
Circuit Symbol and IC Pinouts
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Ideal Op-Amp (page 609)
1. The circuitry of an operationalamplifier with a closed, negative-feedback loop will adjust its output inany way possible to make theinverting input and non-inverting inputterminals of the device equal involtage.
2. Infinite Input ImpedanceThe inputs draw no current.
3. The output impedance is zero.
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Inverting Amplifier
How does V out depend in V in?
Is there a phase shift between Vout
and V in?
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Non-Inverting Amplifier
How does V out depend in V in?
Is there a phase shift between V out and V in?
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Voltage Follower
How does V out depend in V in?
Is there a phase shift between V out and V in?
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Difference Amplifier
How does V out depend in V in?
Is there a phase shift between V out and V in?
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Chapter 14
OperationalAmplifiers
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Junction Field Effect Transistors
JFETs performs some of thesame operations as BJTs butthey constructed differently.
It also has three terminals SourceDrain
GateCircuit Symbols
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Junction Field Effect Transistors
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Transistor ConfigurationsCommon EmitterCommon Collector
Common BaseEmitter FollowerDarlington ConfigurationTransistor Switch
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2003 Notes
Shockley Equation on ExcelSee Homework Problems