Re: really low power transistors

On Fri, 19 Dec 2008 18:49:06 -0800, mrdarrett wrote:

On Dec 19, 4:19 pm, Tim Wescott <t...@xxxxxxxxxxxxxxxx> wrote:
On Fri, 19 Dec 2008 13:45:04 -0800, mrdarrett wrote:
Anyone recommend any NPN transistors with around 0.1-0.3VBE sat. ?

I did a mouser search but apparently Vbe sat. isn't a commonly
specified parameter... ?

Thanks,

Michael

Base to emitter voltage at saturation?


Yes, that.



Or do you mean Vce_sat, the _collector_ to emitter voltage at
saturation?


No, not that.

Zetex and others make the latter in small sizes. The former can't be
done in silicon.


Ah.

Mr. Larkin had an interesting idea. If I wanted to say power a boost
converter (0.1 V to 1V) could I just feed the 0.1V to the base of my,
eh, 2N3904 NPN and it would work (at just incredibly low efficiency,
since it's not in saturation)?

You probably won't be able to detect the difference in collector current
between Vbe = 0 and Vbe = 0.1, at least with a Silicon transistor. Even
a Germanium transistor really needs a Vbe of around 0.3V. So there's not
much difference here between using a 2N3904 and a lump of clay.

You ask for the impossible. Explain what you _really_ want to do, and
someone may be able to help you out.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
.

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