really low power transistors

Most any npn will do that at low current.

John

Either the OP has got the terms mixed up or wants a germanium transistor.

Yeah, low power isn't necessarily equal to low Vbe_sat, but I figured a 0.1Vbe_sat transistor wouldn't be an output transistor in a 100W audio amplifier anyway...

Thanks.

Michael

...

What a coincidence - I just subscribed here to ask that exact question. Well, my question's a little more complicated, so I'll do another thread for it.

As to your question - I found low Vcesat ... oh, wait - you wanted low V_be_sat. Or did you? Anyhow, ON Semi has SMT BJT's down to 50 mv Vcesat:

HTH, Bob

The trolling fool wants Vbe sat to be impossibly low.

... Phil

When I don't have that info in front of me, I usually go for a low Vceo range, the Vsat is normally lower.

Your search is average for a unit in the 20 Vceo range.

Base to emitter voltage at saturation?

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

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

Vbe ?

Do you mean Vce ? Shouldn't be a problem. 2N4401 2N4403 are very low IIRC. Mind you @ what current ? You're really not supplying enough info.

Graham

You're talking nonsense.

Graham

Yup 50mV is no trouble.

Graham

Yes Zetex has about the best low VCE sat BJT's that I've found. The FMMT491 and FMMT618 to name two.

Onsemis got a couple too the NSS40201LT1G and the NSS40301MZ4 they're a little pricey though.

Yes, that.

No, not that.

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)?

Thanks,

Michael

Yes.

No.

Shouldn't be a problem. 2N4401 2N4403 are very low

@ < 100 mA. Not expecting much @ 0.1V.

Actually the 0.1V was kind of optimistic, come to think of it...

Michael

Oops, I was thinking Vce. Even a germanium won't do that low a Vbesat.

What does Vbesat mean anyhow?

We're using some cool phemts (gaas fets) that are, like, 4 ohms Rdson at zero gate voltage, and essentially off at -0.5.

John

A 0.1 volt input boost converter would be a challenge. The easy way would be to bootstrap it with a battery. Or a solar cell.

You might be able to make an oscillator, at 0.1 volts, from a depletion-mode gaasfet. Maybe.

Too bad you can't get tunnel diodes any more.

John

Vbe with collector open?

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.

Funny. I would have thought they are common. Guess I was wrong.

Anyhow... I was thinking of making some sort of super-tiny electric generator (basically just a magnet loosely moving inside a coil of wire), and boosting that up to, oh, 1 volt or so, to light up an LED. Another challenge would be to rectify the tiny current... guess I can't use normal diodes (0.7V drop... oh well...)

Michael

No, it wouldn't work at all, unless what you have in mind is different than what you seem to be saying. Give us a schematic of what you are thinking about.

Ed