Baxandall Class-D Oscillator paper accessible on my web-site

Many thanks to you and the IRE for that.

very interesting, when did the transistor rotate its collector/emitter ??

hamilton

It must have been very soon thereafter - I was using the modern transistor symbol in 1966.

-- Bill Sloman, Nijmegen

It must have been very soon thereafter - I was using the modern transistor symbol in 1966.

-- Bill Sloman, Nijmegen

Thanks for the Baxandall info Bill. Also, my old Motorola transistor data book from 1958 has the transistor drawn as it is today. Regards, Tom

On a sunny day (Wed, 25 May 2011 06:24:54 -0700 (PDT)) it happened Bill Sloman wrote in :

Actually that transistor symbol very much looks like the old Ge transistors were made, a small square base plate, with a big drop of Ge on each side. Indium too?

collector | . . . . . . ========= ---------- base . . . . | emittor

I am not sure, but I think the collector was a bigger blob. You could see it if you scraped the paint of an old OC13 for example.

were made,

That's an alloy diffused transistor. The base is a slab of n-type germanium, and the pellets are indium. The pellets were melted into the slab, which diffused the indium into the crystal. Indium made both the dopant and the emitter/collector contacts.

John

Thanks Bill!

Your web site seems to be about the only place on the Internet where the thing is discussed directly (only getting indirect coverage from, e.g., Jim Williams' app notes that you cite).

---Joel

thing

It is a specialised circuit with relatively few practical applications, and it involves a transformer, which frightens off most people.

I found it cute when I first came across it in 1968, but I think I've only used it twice since then, and the version I invented in 1986 is a tolerably radical reworking of Baxandall's basic idea.

-- Bill Sloman, Nijmegen

Nice. Thanks Bill!

Ed

His Fig.8. looks almost identical to the circuit of low energy light bulbs. The only significant difference is the load, which is across part of the series-tuned circuit in the light bulb so that the off-load resonance builds up enough voltage to strike the tube.

It was a British Standard at the time.

There was a lot of discussion in the pages of Wireless World about the most appropriate symbols to represent different transistor structures when new types first began to appear on the market. You will find the 'horizontal base' symbol in many U.K. manufacturers' drawings at the time and, because Baxandall worked for a government research department, he would have had to stick to the British Standard (whether he liked it or not).

On a sunny day (Thu, 26 May 2011 10:35:10 +0100) it happened snipped-for-privacy@poppyrecords.invalid.invalid (Adrian Tuddenham) wrote in :

Yes, but why did they chose for the 'point contact transistor' ? LOL

There are lots of British Standards that don't make sense.

My impression is that all the sensible ideas have already been suggested by different people by the time the BS Committe meets. The committee is liable to be accused of favouritism if they choose one of the sensible suggestions, so they choose something so outrageously stupid that nobody has ever thought to suggest it.

By comparison with some other British Standards, the use of a point-contact symbol to represent a planar transistor is quite sensible ....at least it is recognisable as a transistor.

Perhaps it was a surface barrier transistor...

The oldest book that I have handy that shows transistor symbols is Terman's classic "Electronic and Radio Engineering", 1955 edition. It uses the modern symbols. Terman was sort of the father of Silicon Valley.

John

collector/emitter ??

Thinking about it again, I don't remember the Emitter and Collector connections being angled like that in the BS symbol.

Yikes, I have the first edition of Radio Engineer's Handbook, 1943, signed by Frederick himself! Formerly owned by Fred J Kamphoefner of Harvard University.

Cool what you can find in a flea market.

A lot of books published around this time were aimed at the war effort. A couple are deliberately deceptive about secrets, like the magnetron.

John

For the first twenty years of my career we used a symbol something like:

PNP: NPN:

E C o o | | ----- +---+ \ / | | \ / +---+ V | |---o B +---+ ----- | |---oB \ / +---+ \ / | | V +---+ | | o o E C

...then didn't use another bipolar for the next 12. ;-)

That was due to the fact that your output device for schematics was limited to line printers, wasn't it? -- No plotters allowed?