Lecture 1: Solid State Devices II.pdf
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The document outlines the history and fundamental concepts of transistors, introduced as a more efficient alternative to vacuum tubes for controlling electrical signals. It describes the structure of transistors, including the terminology of emitter, collector, and base, as well as the two main types: npn and pnp. The transistor's role as a semiconductor device that amplifies signals while consuming less power is emphasized, highlighting its advantages in electronic applications.
Lecture 1: Solid State Devices II.pdf
- 1. B.Sc. II Dr. Vaishali V. Deshmukh Dept. of Physics Shri Shivaji Science College, Amravati Solid State Devices-II
- 3. Transistor history, Why called transistor? Introduction 01 Emitter, Collector, Base. Types Transistor Leads 02 Some facts about the transistor 03 Working of npn and pnp transistor Transistor Action 04 Outline
- 4. Introduction The crucial component of an electronic device is a controllable valve that lets a weak signal control a much larger flow much as a faucet controls the flow of water. At one time the controllable valve used in electronic circuits was the vacuum tube. The vacuum tube worked but it was bulky and used a lot of electrical power that ended up as heat which shortened the life of the tube itself. The transistor was a much more elegant solution to the needs of electronics. The transistor is small and uses much, much less power than the vacuum tube. Because it uses so little power there is little heat to dissipate and the transistor does not fail as quickly as does a vacuum tube. The transistor was successfully demonstrated on December 23, 1947 at Bell Laboratories in Murray Hill, New Jersey. Bell Labs is the research arm of American Telephone and Telegraph (AT&T). The three individuals credited with the invention of the transistor were William Shockley, John Bardeen and Walter Brattain.
- 5. Transistor Definition: The transistor is a semiconductor device which transfers a weak signal from low resistance circuit to high resistance circuit. The words trans mean transfer property and istor mean resistance property offered to the junctions. In other words, it is a switching device which regulates and amplify the electrical signal likes voltage or current. The transistor consists two PN diode connected back to back. It has three terminals namely emitter, base and collector. The base is the middle section which is made up of thin layers. The right part of the diode is called emitter diode and the left part is called collector-base diode. These names are given as per the common terminal of the transistor. The emitter based junction of the transistor is connected to forward biased and the collector-base junction is connected in reverse bias which offers a high resistance.
- 6. Transistor symbols There are two types of transistor, namely NPN transistor and PNP transistor. The transistor which has two blocks of n-type semiconductor material and one block of p-type semiconductor material is known as NPN transistor. Similarly, if the material has one layer of N-type material and two layers of P-type material then it is called PNP transistor. The symbol of NPN and PNP is shown in the figure below. The arrow in the symbol indicates the direction of flow of conventional current in the emitter with forward biasing applied to the emitter-base junction. conventional current always flows from p-type material to n-type material. The only difference between the NPN and PNP is in the direction of the current. So, in the case of NPN, it is flowing out. In the case of PNP it is flowing in.
- 8. Some facts about the transistor
- 10. Transistor circuit as an Amplifier
- 11. Science is a field which grows continuously with ever expanding frontiers. “The combined results of several people working together is often much more effective than could be that of an individual scientist working alone.”
- 12. THANK YOU