How Does a Transistor Work?


How does a transistor work? Our lives depend on this device.
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When I mentioned to people that I was doing a video on transistors, they would say “as in a transistor radio?” Yes! That’s exactly what I mean, but it goes so much deeper than that. After the transistor was invented in 1947 one of the first available consumer technologies it was applied to was radios, so they could be made portable and higher quality. Hence the line in ‘Brown-eyed Girl’ – “going down to the old mine with a transistor radio.”

But more important to our lives today, the transistor made possible the microcomputer revolution, and hence the Internet, and also TVs, mobile phones, fancy washing machines, dishwashers, calculators, satellites, projectors etc. etc. A transistor is based on semiconductor material, usually silicon, which is ‘doped’ with impurities to carefully change its electrical properties. These n and p-type semiconductors are then put together in different configurations to achieve a desired electrical result. And in the case of the transistor, this is to make a tiny electrical switch. These switches are then connected together to perform computations, store information, and basically make everything electrical work intelligently.

Special thanks to PhD Comics for awesome animations:

And thanks to Henry Reich and Vanessa Hill for reviews of earlier drafts of this video.

Music: Kevin MacLeod ( Decisions


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  1. So… I was assigned to watch this video as part of an online class, and turns out I had already liked the video from… who knows how long ago.

  2. Now I know P does not equal to + and vice versa… Thanks for the clearing this up with a nice demo. Watched over 10 videos and can't understand how you get + and – charge carriers…

  3. So … what is the switch that is used to apply the small positive voltage to the gate that makes the transistor act as a switch?

  4. Fair play. I am an electrical engineer with a Bachelors and Master degrees. If I had videos like this whilst studying, life would have been so easy. It's nice to sit back and watch these videos knowing that my visualization and thinking was correct, if not hard earned.

  5. 1:17 How would the Silicon atoms bond together? They can not give or take any electrons so the only option is sharing. If they were to share a valance shell how would that even work?

  6. At, 2:26 holes are more than that of electron(they are not lesser than electron)
    Because you're doping it with boron which is trivalent
    I got the point you were making but,no if holes responsible for( conduction ) is greater than no of electrons responsible for conduction.


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