Science Technology

Jeri’s at it again, this time, cracking open some 1N34 diodes to harvest the germanium to build a crude transistor. Before that, she does a really nice job sketching out the basic physics behind semi-conductor operation. And she does get her point-contact transistor to work. Crude, but it works! Kudos, as always, Jeri!

Make a Point Contact Transistor at Home

Lost Knowledge: Homemade electronic components

8 thoughts on “Jeri homebrews some point-contact transistors

  1. Oooo how I hate the thought of electrical holes – What’s wrong with the essential logic that electron flow is from Negative to positive rather than hanging onto ‘archaic’ conventional flow concepts.

    1. First off, holes only exist in semiconductor devices, and don’t have anything to do with our nomenclature for charge.

      It is important to make a distinction between holes and electrons in semiconductor physics, because electrons in different energy states ( have different mobilities ( So, even though holes are just the absence of an electron, they have different properties and have to be considered separately.

      1. What we are discussing is only a model of what happens as electrons are, depending on your viewpoint, negativity charged particles with a mass approx 1/1836 of a proton or a vibrational field who’s position/mass in space can only be described by probability.

        Both of these are supportable by experimental evidence.

        Electron Holes on the other hand are simple a conceptual convenience (

        Whereas I don’t deny that the educational and engineering world has been using holes since the 1940’s to describe their models of what happens in electronics that doesn’t give them any reality just a convenient way to discuss electronics using conventional current flow. One can just as easily model by saying that when an electron jumps from atom to atom it leaves behind a space that can be filled by another electron from another atom. It’s a viewpoint and visualisation aid that’s all. (

        As a teacher I can assure you it is MUCH easier for students to understand and accept that an electron has a neg charge and is therefore repelled by a neg charge and attracted by a positive charge. rather than introduce semi mythical ‘holes’ into the story/model.

        However each to there own I guess and although now in my 60’s and originally taught hole models as a model for transistor theory in the 1960’s as a trainee electronics engineer I realised how much easier it was to look at things from an electron point of view when I had to teach the subject.

  2. I have re-read my comments and whilst I still stand by the electron/hole issue I wanted to say I think this is a great thing to do Jeri, I didn’t want to come across sounding like I dumped on the whole thing.

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Gareth Branwyn is a freelance writer and the former Editorial Director of Maker Media. He is the author or editor of over a dozen books on technology, DIY, and geek culture. He is currently a contributor to Boing Boing, Wink Books, and Wink Fun. And he has a new best-of writing collection and “lazy man’s memoir,” called Borg Like Me.

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