as a scr equvalent circuit shows is there any way to make a scr from two bjt transistors

 

as a scr equvalent circuit shows is there any way to make a scr from two bjt transistors

You can, but it won't behave the same as an actual SCR because the geometries won't be the same.

Image from wikipedia:

https://en.wikipedia.org/wiki/Silicon_controlled_rectifier

 

Equivalent circuits are idealizations, and an aid to analysis and understanding. They may or may not work the same as an actual device. By all means, feel free to test the hypothesis that two transistors might bear some relationship to an actual SCR. Let us know what you discover.

 

You can, but it won't behave the same as an actual SCR because the geometries won't be the same.

Image from wikipedia:

https://en.wikipedia.org/wiki/Silicon_controlled_rectifier

its close enough for most practical purposes - and the "other" gate makes it a programmable unijunction. More accurately - its an SCS which gives you both gates. Its good for generating sawtooths and/or narrow pulses, but its usefulness as a power SCR tail off fairly quickly.

 

as a scr equvalent circuit shows is there any way to make a scr from two bjt transistors

Yes and no. Unlike trying to make a transistor using two back-to-back diodes (which doesn't work at all because of the need to have a very thin base region separating the collector from the emitter), you can make an SCR using two discrete transistors, but it will behave quite differently in many respects from an integrated one. For some applications it will be useful and for others it will not.

 

The very foggy region with thyristor-like characteristics one may get indeed (or at least dinistor like), but knowing the aim of SCR is kilowatts at near kilovolt, the whole idea sound me as "how to make a vacuum tube pentode from couple of triodes tubes?" The available answer is noway-how. That thyristor Yo`ll get will be <<garbage thyristor>> and to get the symistor aka triac You will crack the neck. Dont! Its better to see You alive and joyful.

 

https://electronics.stackexchange.com/questions/141987/how-can-i-create-an-scr-using-a-pnp-and-npn

http://circuitdigest.com/sites/defa...m/simple-transistor-latch-circuit-diagram.png


Regards, Dana.

 

RE: Danadak
Yes, we can. We can even build a water pump from just two ale-cans, but does it will happen to be good, trustable and efficient water pump to rely-on. The scr made on bjts the solely benefit is damn fastness while most of scr are damn slow, except the few. But if the aim is to produce the product what peaople may trust-on, then bjt instead of scr is nightmare, Instead of scr must stay the scr of course. It cost the same money, there is no ANY economy to exchange the real thing with garbage and drink the champain. Champain for what? For making the circuit bad?

 

Totally agree, buy an SCR. Reason for my previous post was to directly answer
the OP's question, one can build latching circuits thru feedback with simple
transistors.

Regards, Dana.

 

RE: Danadak
Yes, we can. We can even build a water pump from just two ale-cans, but does it will happen to be good, trustable and efficient water pump to rely-on. The scr made on bjts the solely benefit is damn fastness while most of scr are damn slow, except the few. But if the aim is to produce the product what peaople may trust-on, then bjt instead of scr is nightmare, Instead of scr must stay the scr of course. It cost the same money, there is no ANY economy to exchange the real thing with garbage and drink the champain. Champain for what? For making the circuit bad?

My very first DIY light dimmer was - and one of them germanium. An OC139, AFAICR: anything over OC199 was silicon.

 

I have built SCR's using very high frequency transistors to make fast risetime pulsers. I found that I had to add a resistor between the base and emitter of the PNP to make it work.

See this link:
https://forum.allaboutcircuits.com/threads/fast-risetime-falltime-pulsers.124518/#post-816114

The circuit shown has both an SCR equivalent and a PUT equivalent: