Crystal Triode

The name transistor was not coined immediately after it was discovered. “Hey, look! It is an … a… errh… transistor!”. Instead there were other alternatives [from a Bell Labs memorandum]: “semiconductor triode”, “solid triode”, “surface states triode”, “crystal triode” and “iotatron”. (I like the last one… it’s futuristic.)

Reading those old books again: analogies

I am once again refurbishing my room to get some more air. These old gems pop up. Books from the beginning of the 1900s (which I have discussed before in previous posts) that describes electricity in a beautiful manner. Hand-drawn, explicit drawings illustrating how for example electricity can be seen as a closed water system. Width of pipes illustrate resistance. Pumps illustrate current sources and water tanks (or centrifugal pumps) illustrating voltage sources.

Parallel and series connection of resistors are illustrated by pipes and gives the reader a good idea of what is happening also in electrical networks.

The water pipe analogy sort of ends there, but at least a good starting point. Good analogies are further described here: by Dr. Douglas Wilhelm Harder. Here is it shown how capacitance can be generated using a flexible membranes in the pipes. The inductor can in turn be modeled as a rotating wheel (turbine-ish). Follow the link and notice how also an LC tank can be modelled. And the brilliant Water-emitting diode (or fountain-emitting 🙂 as coined by Dr. Harder. ).

Back to the topic: transistors

So, resistor [check!], inductor [check!], capacitor [check!], voltage source [check!], current source [check!], and diode [check!]. Analogies done. What about the transistor? Well, that’s sort of already done and in some sense quite intuitive: the tap, or a water lock or valve driven by another stream of water. These analogies have been around and an animated version is found here:

Looking a bit deeper into the transistor. These two pages from the 1954 book “Crystal rectifiers and transistors” edited by M.G. Say (Whitefriars Press Ltd.) which I have copied and reproduce here without really asking for permission. Fingers crossed that no one gets upset… In turn the pictures have been reproduced by permission from the RCA Photophone Ltd.

This page shows a neat description of the point-contact transistor and the junction transistor. Notice the “subtle” differences in the way the transistors are constructed. Also notice that these transistors pre-dates the planar process (1959) and the mesa transistor (1958).

To the left we can envision how a small current (well, a certain voltage must be applied and a varying voltage creates a current-flow) applied on the left-hand side – between the emitter and base – “pulls” electrons through the collector effectively creating a large current and amplifies the voltage. In more recent text books, these currents are just illustrated by large arrows and it gets too abstract IMO.

People do not tend to have the time to draw small round circles anymore… hmm…

The point-contact transistor was the one Bardeen, Brattain and Shockley demonstrated during Christmas 1947 (and published in June 1948). We also find the junction transistor at the bottom of the page. Perhaps a bit more complicated to decode the picture there. The junction transistor was invented by Shockley in 1950 (i.e., just four years old in the printed version of this book) and the operation is fundamentally (well…) different from the point-transistor.

The right-hand page shows the physical implementations back then (i.e. the “Diagrammatic sketches”). A bulky device encapsulated in a plastic case. The pictures quite clearly illustrate the physical differences between the point-contact and the junction transistors.

The junction transistor was more reliable (to the cost of more semi-conducting material) and could be commercialized much more quickly.

More physical descriptions of the implementation of the point-transistors are given in the book: “practical” implementations that could be integrated with the existing systems back then. (Only 60 years ago…)

So the name?

There seems to be a few different suggestions to the term transistor and I guess people’s memories tend to fail when it comes to remembering who coined the name to one of the greatest inventions in mankind. John R. Pierce is attributed to the coining of the term and as per his description (my interpretation): “there should be something with ‘trans’ in it from transconductance. It should align with the rest of our product portfolio, i.e., -istor: Transistor.”

All other explanations just sound too complex… Still though, iotatron would be a cool name!

At Bell, they actually voted for the name and there is a memorandum (where there is yet a etymological description of “transistor”) with 25-odd names on. The list included, of course, the above mentioned Shockley, Bardeen, Brattain, and Pierce, but also other giants like

  • Frank Gray (the Gray code),
  • CB Feldman (bandwidth-vs-transmission performance, i.e., Shannon’s aid to find the channel capacity),
  • ME Mohr (designed the first-ever quantizer)
  • JO Edson (contributor to the pulse-code modulation technique for speech coding)
  • WE Kock (developed some of the first electronic musical organs)
  • JN Shive (inventor of the Shive wave machine – see below, which elegantly illustrates travelling waves in electronics)
  • [Edit, how could I forget the target of one of my previous posts] HS Black (inventor of the negative feedback amplifier)

One thought on “Crystal Triode

  1. Pingback: Feedback – a quick overview | Mixed-Signal Comments

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