Jeri homebrews some point-contact transistors

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. Rick says:

    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. Matt Mets says:

      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. Rick says:

        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. Rick says:

    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. His free weekly-ish maker tips newsletter can be found at

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