Morgan Olsson wrote:
>
> Thank you for your work Roman, this Black regulator really look nice :)

Thank you! :o)

> >I think I would use 2x BC327 in parallel and 2x 1N5819
> >in parallel.
>
> Warning: Parallelling bipolar transisotrs is usually avoided, since their temperature characterstic will make only one of them operate:  Th eone whichis slightly warmer wil have lower Ube, so, it do more labour than the other, and get still warmer etc.  Finaly you have one very hot tranny and the other just sitting there.  Solution: use separate base resistor(s).

Yes, apart from you need 2 emitter resistors (not base)
as base resistors will have the wrong effect. :o)

> Parallelling bipolar diodes i have never seen, may be same problem, but cheaper to use one bigger eanyway.  But for shottkys like 1N5819 i have done and no problem.

That's good to hear, thanks!


> >This is still smaller and cheaper than
> >just about any alternative.
>
> Maybe Bc640-16.  (that -16 defines hFE=100..250, plain Bc640 is only 40..250 which would require designing for higher base drive margin)
>
> Btw for even cheaper design use i.e Bc546B for Q2.

Thanks again for the suggestions.

> Possible problem: verify peak negative Ube of Q2.  I fear that for higher input voltages it will be over spec (which usually is 5V for transistors like theese)  Problem is when it switches off, and C2 pulls it far down.

Yes I anticipated this problem, the ratio of C1:C2
capacitances determines how far C1 will discharge
during the turn-off phase, and this is set at 3.0v
so the base is exposed to (3.0v - 5.0v(regulated))
= -2v
This should be within spec for the circuits I showed.

With larger power circuits I suggest trying a resistor
in series with C2 to limit dump current.


> Side note: all paragraphs on i.e http://www.romanblack.com/a02.htm gets line wrapped in browser Opera, making a mess of ASCII art and test data. (NO paragraphs

Thanks and sorry about that. I chose to use the text
circuit as it is easy to edit. I don't think the line
width can be reduced. Can you change Opera to allow
longer line widths?
-Roman

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu