Electronics > Projects, Designs, and Technical Stuff
Having fun with discrete transistors
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schmitt trigger:
The key to run bipolar transistors that fast was to keep them out of the saturation region.....consumed a lot of power though!
soldar:

--- Quote from: schmitt trigger on January 10, 2019, 09:16:14 pm --- 2N2646 unijunction transistors.
--- End quote ---
Gosh, I still have a few which I have kept over the decades... I believe I have not used one in decades nor seen any new designs using them. Are they even made any more? I doubt it.  They are really of very limited use and 555 chips or others can be substituted with advantage. 
schmitt trigger:
The 2N2646, having a metal can, has long been obsolete.

The plastic versions 2N4870/ 2N4871 are still available. Though not widely available.
james_s:
I like UJTs, I remember using them to build lamp flashers, it can be done very easily.

I have an old Heathkit wind speed/direction display that uses a UJT based oscillator to clock the display latches.
Circlotron:
Next, how about an oscillator using an SCR and a resonant tank? These kinds of circuit techniques are becoming lost in the sands of time. And what about a tunnel diode doing something?
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