Look this FIRST point-contact transistor, is it NPN or PNP? Can I make one?

[Willen]

Hi,
First question is- PNP or NPN this Point-contact Transistor is? How it is NPN or PNP?

Second and main question is can I make this one using a germanuim chip and two collectro and emitter contacts of graphite or any sharp metal? I have a 1x1 cm germanium chip taken out from a germanium diode. Can I get a transistor function and can I get hFE (even so less) on miltimeter? So excited forever with these Vintage electronics! Say something please!

IMAGE: https://en.m.wikipedia.org/wiki/Point-contact_transistor

 

[mvs sarma]

i presume it was pnp

 

[Mike odom]

Yes, PNP, and of the common base type amplifier (not the common emiter used so frequently today).

 

[MrAl]

Hi,

I mad a point contact diode back a long time ago using iron oxide and a sharp needle. Many people did this actually and it's not hard to do but takes a little patience to get going.
I never got around to doing it with a transistor though.

People make all sorts of home made devices like this, including solar cells. I would not bet on how good they are though, but it may be interesting anyway just to see how it works first hand.

It's too bad that many experiments done today have to be in a lab with expensive equipment and a good budget to be able to afford precise machining and whatever is needed to construct good projects. The LHC being the best example.

 

[mvs sarma]

common base is used even now in RF amplification,

 

[Willen]

Yes, a months ago I too made a foxhole radio. So I made Home made point contact diode using oxidized razor blade and sharp graphite (pencil). Got nice diode. But transistor is more complex to make and to understand for me. So want to make myself and want to see its hFE on multimeter.

How it would be a NPN then?

 

[unclejed613]

http://semiconductormuseum.com/MuseumLibrary/HistoryOfTransistorsVolume1.pdf