History and Functioning of Transistors: From Vacuum Tubes to Solid State Devices, Slides of Engineering Physics

Download History and Functioning of Transistors: From Vacuum Tubes to Solid State Devices and more Slides Engineering Physics in PDF only on Docsity!

Transistors

CONTENTS

1. HISTROY

2. WHAT IS TRANSISTOR

3. TYPES OF TRANSISTOR

4. APPLICATIONS OF TRANSISTORS

5. TRANSISTOR AS AN AMPLIFIER

• Joseph John Thomson developed a vacuum tube to carefully investigate the nature of cathode rays, which resulted in his discovery, published in 1897.
• At the same time as physicists were trying to understand what cathode rays were, engineers were trying to apply them to make electronic devices. In 1906, an American inventor and physicists, Lee De Forest, made the vacuum tube triode, or audion as he called it. The triode was a three terminal device that allowed him to make an amplifier for audio signals, making AM radio possible. Radio revolutionized the way in which information and entertainment reached the great majority of people.

• The vacuum tube triode also helped push the development of computers forward a great deal. Electronic tubes were used in several different computer designs in the late 1940's and early 1950's.
• In 1947, John Bardeen and Walter Brattain, working at Bell Telephone Laboratories, were trying to understand the nature of the electrons at the interface between a metal and a semiconductor. They realized that by making two point contacts very close to one another, they could make a three terminal device - the first "point contact" transistor
• They quickly made a few of these transistors and connected them with some other components to make an audio amplifier
• This invention was the spark that ignited a huge research effort in solid state electronics. Bardeen and Brattain received the Nobel Prize in Physics, 1956,

TYPES OF TRANSISTORS

 NPN TRANSISTOR

 PNP TRANSISTOR

NPN TRANSISTOR

• Transistors where the majority charge carriers are electrons

PNP TRANSISTOR

• Transistors where the majority charge carriers are holes

PNP TRANSISTOR

High potential at emitter

Low potential at collector

Allows current flow when base is connected to a low potential

APPLICATION OF TRANSISTOR

• Transistors are widely used in electronic devices. It is used as:

1. Amplifier
2. Switch
3. Sensor etc.

The Transistor as an Amplifier

• Amplification is the process of linearly increasing the amplitude of an electrical signal.
• The BE (base-emitter) junction has a low resistance due to forward bias and the BC (base-collector) junction has a high resistance due to reverse bias.

TRANSISTOR

I B =VBE /r

I C=BIB

I C=BVBE /r

V O=VCE

TRANSISTOR

by applying KVL

V CC=I CR C + VCE

VCE =VCC - ICRC

As we know

VCE =VO