[SOLVED] Pair of bipolar transistors - crazy connection

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bodzio_stawski

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Hello!

I would like to ask if any of you have come across this type of connection of bipolar transistors:

I don't remember the rest of the circuit - I draw it from my memory. But I am sure about the direction and type of the transistors themselves.

In order to adopt some model of GND, it would have to look something like this:


Regards

Bogdan
 

Hi,

please give all parts in your schematic unique names to avoid misunderstanding.

When there is enough voltage between V2 and V1 then - because of the left resistor - the left BJT becomes conductive.
It´s emitter current goes through the right resistor and cuases a voltage drop. At a certain current the voltage is enough to make the right BJT conductive.
..and then then this reduces V_BE of the left BJT.
--> a current limiter

Klaus
 
As Klaus mentioned, it is a current limiter, might be also thermally coupled pair.
It looks like part of the linear voltage regulator like uA78XX. Check datasheet of this regulator series.
 
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