🚀 go-pugleaf

|Most Japanese transistors I've seen use a numbering system that
|starts with a single letter A-D and a few numbers.  The actual part
|number is '2S' followed by whatever is marked on the transistor.
|For example, the part number you should look for is 2SD1439/65.
|For some reason, they never put the '2S' on the package.
|
|As far as I've seen, 2SA and 2SB parts are PNP, while 2SC and 2SD are NPN.
|(Someone prove me wrong on that one...)

In another life I had a Japanese transitor data book (in Japanese). The
numbers and letters actually mean something. (This is not surprising
given that electronics engineers like neat classifications. :-)) The
first number is the number of junctions, hence 1=diode, 2=transistor.
The second letter means (I think)

	A, B = germanium
	C, D = silicon

I'm not positive of this. I also forgot what the A/B and C/D difference
is.  (RF/audio?) Somebody please post the right info. It just so
happens that most germanium transistors are PNP and most silicon are
NPN.  The final number is just a registration number, assigned
serially.

The European system is similar. The first letter is: A=germanium,
B=silicon.  (I'll bet they have one for GaAs too.) The second letter is
the class of device, e.g. C=general purpose, F=junction FET. Then
follows a registration number. The final letter is for variants of the
same transistor (e.g. gain groups: they used so sort them by this and
sell the higher gain ones for more).  U in the second position is, I
seem to remember, for deflection/video drive transistors, hence it's
important to get one with adequate specs if you don't want to release
the smoke particles they have marvelously packed into such a small
package :-).