new

1. 1
NAME: ESTHER UYO OJO LABIJA
REG NO: 2007252052
COURSE: COMPUTER HARDWARE MAINTENANCE COM 223
DEPT: NDII COMPUTER SCIENCE
QUESTION:
EXPLAIN EXTENSIVELY ON THE TERM TRANSISTOR
WHITE SHOT NOTE ON SERIES AND PARALLEL CIRCUIT
INTRODUCTION
Transistors make our electronics world go 'round. They're critical as a control source in
just about every modern circuit. Sometimes you see them, but more-often-than-not
they're hidden deep within the die of an integrated circuit. In this tutorial we'll introduce
you to the basics of the most common transistor around: the bi-polar junction transistor
(BJT).
WHAT IS A TRANSISTOR?
A transistor is a type of electronic device which is formed by p-type and n-type
semiconductors. When a semiconductor is positioned in the middle of two
semiconductors of the same type then this arrangement is called the transistor.
 A transistor can also be defined as a simultaneous connection of two diodes.
 A transistor is a device that controls the passage of current or voltage and serves
as a button or gate for electronic signals.
 It has three terminals namely emitter, base and collector.
 Transistors have had a significant impact on the electronic industry's revolution.
 It is capable of signal amplification as well as signal rectification.

2. 2
TRANSISTOR DEVELOPMENT
Semiconductor technology is now well established but it has been used for over a hundred
years. The first semiconductor effects were noticed back in the early 1900s when the first
wireless or radio sets were being used. Various ideas were being investigated as
detectors.
Thermionic valve or vacuum tube technology was introduced in 1904, but these devices
were expensive, and also required powering by a battery. Soon afterwards the Cat's
Whisker detector was discovered. This consisted of a thin wire placed onto one of a
number of types of material. These materials are known today as semiconductors and
form the basis of modern electronics technology.
BASIC TRANSISTOR STRUCTURE
The transistor is a three terminal device and consists of three distinct layers. Two of them
are doped to give one type of semiconductor and the there is the opposite type, i.e. two
may be n-type and one p-type, or two may be p-type and one may be n-type.. They are
arranged so that the two similar layers of the transistor sandwich the layer of the opposite
type. As a result these semiconductor devices are designated as either PNP transistors
or NPN transistors according to the way they are made up.
Basic structure and circuit symbols for NPN & PNP transistors
The names for the three electrodes widely used but their meanings are not always
understood:
 Base: The base of the transistor gains its name from the fact that in early
transistors, this electrode formed the base for the whole device. The earliest point
contact transistors had two point contacts placed onto the base material. This base
material formed the base connection . . . and the name stuck.
 Emitter: The emitter gains its name from the fact that it emits the charge carriers.
 Collector: The collector gains its name from the fact that it collects the charge
carriers.

3. 3
TYPES OF TRANSISTORS ARE LISTED BELOW:
 Bipolar Junction Transistor
 Diffusion Transistor
 Avalanche Transistor
 Schottky Transistor
 Darlington Transistor
 Heterojunction Bipolar Transistor
 Field Effect Transistor
 Junction FET Transistor
 Dual Gate MOSFET
 Multiple-Emitter Transistor
Bipolar Junction Transistor (BJT)
These are current-controlled devices and are of two types NPN and PNP. In NPN, the
majority of the current is carried by electrons. In PNP, the majority of the current is carried
by holes.
Diffusion Transistor
These are one type of BJT and is formed by diffusion of dopants into a semiconductor
substrate. For example, Philco’s micro-alloy diffused transistor.
Avalanche Transistor
It is one kind of Bipolar Junction Transistor which process the region of collector-
current/collector-to-emitter voltage and which is beyond the voltage of the breakdown of
collector-to-emitter also called avalanche breakdown voltage. The operation here is called
avalanche-mode operations which is, it switches between high currents in less than
nanoseconds.
Schottky Transistor
When a transistor is combined with a Schottky diode, it is called Schottky transistor.
Introducing that type of diode prevents the transistors from saturating by the diversion of
extreme input current.

4. 4
Darlington Transistor
It is a transistor circuit made from two different transistors. It has a higher ability to gain
current. Its circuit can be inside an integrated circuit also.
Heterojunction Bipolar Transistor (HBT)
These types of transistors are used in analog or digital microwaves with higher frequency.
It provides faster switching speeds and provides better lithographic yield. They present
better emitter injection efficiency.
Field Effect Transistor (FET)
These are voltage controlled and have high input impedance which causes little current
to pass through them. They are unable to provide the same type amplification as BJTs.
Junction FET Transistor
This type of FET transistors has no PN junctions but a majority of current flows through
two electrical connections at either end called the Drain and Source respectively. These
are of two types N-channel and P-channel.
Dual Gate MOSFET
It operates as two MOSFET devices in series. There are two gates which is made-up
along the length of the channel. Both gates affect the general MOSFET operation and the
output.
Multiple-Emitter Transistor
Here, the emitters are applied with input signals. It can reduce switching time and power
dissipation.
These were some types of transistor if you wish to know more, download BYJU’S The
Learning App

5. 5
QUESTION 2
SERIES CIRCUIT
A circuit is said to be connected in series when the same current flows through all the
components in the circuit. In such circuits, the current has only one path. Let us consider
the household decorative string lights as an example of a series circuit. This is nothing
but a series of multiple tiny bulbs connected in series. If one bulb fuses, all the bulbs in
the series do not light up.
PARALLEL CIRCUIT
A circuit is said to be parallel when the electric current has multiple paths to flow through.
The components that are a part of the parallel circuits will have a constant voltage across
all ends.
Difference Between Series and Parallel Circuits
Series Parallel
The same amount of current flows through
all the components
The current flowing through each
component combines to form the current
flow through the source.
In an electrical circuit, components are
arranged in a line
In an electrical circuit, components are
arranged parallel to each other
When resistors are put in a series circuit, the
voltage across each resistor is different even
though the current flow is the same through
all of them.
When resistors are put in a parallel
circuit, the voltage across each of the
resistors is the same. Even the polarities
are the same
If one component breaks down, the whole
circuit will burn out.
Other components will function even if
one component breaks down, each has
its own independent circuit
If Vt is the total voltage then it is equal to V1
+ V2 +V3
If Vt is the total voltage then it is equal to
V1=V2=V3

6. 6
REFERENCE
Resnick, Robert; Halliday, David (1966). "Chapter 32". Physics. Vol. I and II (Combined
international ed.). Wiley. LCCN 66-11527. Example 1.
Smith, R. J. (1966). Circuits, Devices and Systems (International ed.). New York: Wiley.
p. 21. LCCN 66-17612.
Costanzo, Linda S. Physiology. Board Review Series. p. 74.
Ellerman, David Patterson (1995-03-21). "Chapter 12: Parallel Addition, Series-Parallel
Duality, and Financial Mathematics". Intellectual Trespassing as a Way of Life:
Essays in Philosophy, Economics, and Mathematics (PDF). The worldly
philosophy: studies in intersection of philosophy and economics. G - Reference,
Information and Interdisciplinary Subjects Series (illustrated ed.). Rowman &
Littlefield Publishers, Inc. pp. 237–268. ISBN 0-8476-7932-2. Archived (PDF) from
the original on 2016-03-05. Retrieved 2019-08-09. […] When resistors with
resistance a and b are placed in series, their compound resistance is the usual
sum (hereafter the series sum) of the resistances a + b. If the resistances are
placed in parallel, their compound resistance is the parallel sum of the resistances,
which is denoted by the full colon […] [1] (271 pages)
Ellerman, David Patterson (May 2004) [1995-03-21]. "Introduction to Series-Parallel
Duality" (PDF). University of California at Riverside. CiteSeerX 10.1.1.90.3666.
Archived from the original on 2019-08-10. Retrieved 2019-08-09. The parallel sum
of two positive real numbers x:y = [(1/x) + (1/y)]−1 arises in electrical circuit theory
as the resistance resulting from hooking two resistances x and y in parallel. There
is a duality between the usual (series) sum and the parallel sum. […] [2] (24 pages)