'Users Still Cautious About Tunnel Diodes' is the headline of a story in Electronics Weekly's edition of April 19th 1961. The story, wirtten by one of my predecessors as Components Correspondent, starts: 'While at the Footscray works of Standards Telephone and Cables I saw some of the application work which is now going on with the tunnel diode.'
'In the hands of the engineers I saw many examples of its versatility including logic systems and CW applications,' adds the Correspondent.
'Among the latter were a stabilised front end amplifier for a Band II receiver, a type of synchrodyne receiver and an age system for control tunnel diodes.'
The story continues: "But", said Mr Alexander, one of the applications engineers, "we are still in the process of overcoming resistance to the use of tunnel diodes for commercial applications."
The story concludes: 'From Mr Alexander's remarks it appears that many design engineers feel that they have not fully exploited the transistor yet and so they are cautious about moving on to a new device.'
Things stayed much the same; I don't remember anyone getting particularly enthusiastic about them. The only real use I can recall (in T & M equipment, anyway) was to generate fast rise pulses. Their peculiar properties seemed to me to be more of a laboratory curiosity than a technology-changing breakthrough. Unless, of course, you know different.
Peter, fast microwave switches, perhaps?
The only RF switches I've come into contact with are either relay or GaAs types. Maybe radar stuff?
I did hear of a way of using a tunnel diode as an amplifier; I think it involved the use of a circulator, but I've never seen - or heard of - a commercially made one.
Do you remember step recovery diodes, and back diodes? Amazing what falls by the wayside.
Peter, I regret to say I don't.
Sad. I don't suppose they even made it to the science museum.
There were many other semiconductor devices that had a very short commercial life, but which are now all but forgotten; indeed, I've forgotten most of them myself. I vaguely remember a static-sensitive germanium transistor from about forty-five years ago. Low power, high frequency and high gain - it was going to change the world!
There's a research project there for some keen historian!
Yes indeed, Peter, it would be a fascinating study. Why were they built? What were they used in? Why did they stop being used? What did they morph into? It would be a great study.