Instruction 7-5

Predict the Voltage of Current | Ohm's Law Problems | Kirchoff's First Law | Kirchoff's Second Law | Transistors | Summary

On Dec. 23, 1947 William Shockley demonstrated the first transistor at Bell Labs.

The transistor has since entirely revolutionized electronics and almost completely replaced vacuum tubes.

As the semiconductor technology improved, the technology of transistors grew making them faster, cheaper, smaller and more reliable.

Transistors have become a technology that is greatly taken for granted. They are a part of almost any electronic device and yet we do not hear about them very often.

Every major modern innovation has been made possible by the transistor. Without it we would not have innovations such as satellite broadcasting, color television, touch-tone dialing, photocopy machines, video cameras and many more advances in technology.

Transistors are most commonly known for their contribution to the world of computers. Almost every component of a computer is controlled by transistors.

In 1959, a breakthrough took place when the integrated circuit (IC) was invented. Transistors are the basic elements in IC’s. IC’s have the ability to organize numerous transistors interconnected with circuitry or other electronic components on a single silicon microchip.

Now microprocessors are comprised of millions of transistors. A PC chip, for example, has 3.5 million transistors!

So what does a transistor do?

A transistor regulates current or voltage flow and acts as a switch or gate for electronic signals. A transistor can function as an insulator and as a conductor. It is the transistor's ability to fluctuate between these two states that enables it to switch or amplify. This is very important in computer operations since they are based on millions of extremely fast on-off fluctuations. In fact, when you send a simple e-mail, you use several billion transistors in the process. The transistor is the brains of a computer.

A diode is device that will block current in one direction but allow current to flow in another direction.

A transistor is like two diodes back-to-back. A transistor has three layers of semiconductors while a diode only has two.

A device that uses batteries will often contain a diode to protect the device if you put the batteries in the wrong way. If the batteries are inserted incorrectly, the diode will block current from leaving the battery and protect the electronics in the device.

Video Instruction
*Availability of You Tube video links may vary. eTAP has no control of these materials.

• How Transistors Work [2:00]

• Tutorial On Transistors [6:55]

• Diode Operations [2:37]

for Students, Parents and Teachers

Now let's do Practice Exercise 7-5 (top).

Summary

You have now completed Lesson 7 on Electric Phenomena and are ready to do the Problem and Test sections.

You may wish to review any or all of the topics before answering the questions that follow. You may also wish to obtain additional material from the links below before answering the questions. In addition, I’ve provided the names of a few good books that will help with your learning.

Good luck!

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