What happen with this transistor?

[jan.didden]

I tought that a CCS is a "maximum current limiter". I tought that with 10mA CCS, I can pass 1 to 9mA without problem, but cannot pass 15 or 20mA.

Well, its a current SOURCE, you design it for a specific current, and that is what it tries to do. If it can't, as I said, something's got to give, in this case Vce get down below Vbe until the B-C diode gets forward biased.

(I'll read the rest of your post later, gotto run.)

Jan Didden

 

[ingrast]

.....
. But I don't have equipment to know if this idea will work.
....

Before commiting to invest in equipment. Better yet, before commiting to solder parts toghether, it should be wise to run simulations.
You allready have a computer, don't you? Download LTSpice and play around.
You will not only test your ideas, much more importantly you will be much better equiped to analyze behavior in ways not even in a good workbench you could dream of. Will learn why something does not work as imagined and will be able to test alternatives without burning parts and much faster.

Rodolfo

 

[jan.didden]

[snip]What do you think about this non-turnoff idea?[snip]

Why not put it up in a schematic? Ity is difficult just to follow it from your narrative.

[snip]I've got another dumb question. If a transistor has HFE=50. This means if we put 1mA in the base, the Collector will have 50mA and Emitor will have 51mA.

If we reverse the condition, will the reverse situation occurs? If I push 50mA in the collector, will the base automaticly draws 1mA?

No, it will not work in reverse, unless you connect the base and the collector together, then push current into the collector. The base will then take just enough current to sustain the collector current you're pushing. What happens is that the current you push will increase Vbe, thus create Ib, thus create Ic, thus the Vce (which is here the same as the Vbe) will go down, and you get the balance condition. But it is really cheating, the transistor doesn't really work in reverse.

Jn Didden