A group for those who want to build their own bipolar transistors
Telefunken Experimental Germanium Point Contact Transistor- 1953
JPEG Image - 291.88 kB - 10/19/2018 at 20:55
Before you ask, “Why make your own transistors at home??” – read my Manfiesto for Why.
Most of the homebrew community has been focused on fabricating Field Effect Transistors (FETs) at home. Sam Zeloof and Jeri Ellsworth are probably wiser to try and ‘etch FETs’ because they are much better suited to fabricating Integrated Circuits (ICs). ICs were a real revolution in electronics because they miniaturised sometimes enormous circuits into small, convenient packages. Discrete circuits also do not last as long as integrated circuits, because it is expensive to render them mechanically inert. ICs can be completely encased in plastic, shielding their components from dust, and heat, and other kinds of physical mechanical interference.
But, from studying the work of Ellsworth and Zeloof, and following up on their references, it seems that manufacturing the kind of transistors they have, in the ways they have, may still be too expensive and difficult for hackers. So in this article I am going to argue that one option for hackers is to fabricate not silicon, planar process FETs, but germanium, alloy-junction, Bipolar Junction Transistors.
Alloy-junction BJTs are a much older and more primitive type of transistor to fabricate than the planar process transistors that Ellsworth and Zeloof talk about, but I will argue that alloy-junction transistors present themselves as an attractive option for hackers who cannot afford expensive equipment and materials, and who have to push most of the cost of hacking onto using their own labour in order to get things done.
Alloy-junction transistors are not the earliest and most primitive kinds of transistors, but they are one of the earliest and most primitive. These kinds of transistors are necessarily discrete transistors. I argue they present themselves as an attractive kind of transistor to fabricate at home in a DIY, homebrew setting because:
Now, I will describe the rough process of how to fabricate this primitive type of transistor.
First, a wafer of germanium made of a single crystal is formed. This can be done by yourself with great amounts...Read more »
I got a germanium disc from ebay, and I did a quick test by and found that pointing a scalpel to it it works as a point contact diode!
It is a bit rough but it works!
From someone who discussed with the author of "Instruments of Amplification":
"Friedrichs also had tinkered with cuprous oxide transistors.
What he didn't tell in the book: only one of 10 cuprous oxide transistors had worked as intended,
and they tend to die at 5V+ or so. He wasn't aware of this when testing them with a curve tracer."
But still, 5V is not a crazy working voltage and many circuits use 3.3V.