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really low power transistors

J

Jamie

Jan 1, 1970
0
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
use a op-amp to increase the level.

http://webpages.charter.net/jamie_5"
 
I

ian field

Jan 1, 1970
0
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

Its simply a matter of biasing the transistor to a suitable operating point
and then coupling the coil to the base with a suitably sized capacitor, or
if the coil can be floating just string the coil between the base and the
bias divider.
 
E

Eeyore

Jan 1, 1970
0
Jamie said:
use a op-amp to increase the level.

What an amazingly stupid comment !

How many op-amps run on 100mV ?

Graham
 
E

Eeyore

Jan 1, 1970
0
Tim said:
Study regular physics before you get to device physics...

Yes, I did. And I have the 'S level' to prove it.
http://en.wikipedia.org/wiki/Scholarship_Level
I only got 'Merit' though due to the astonishing lack lack of electronics in
that year's paper.

Semiconductor Physics was one of my favourite courses at UCL. Everyone else
positively HATED it.

Graham
 
J

Jamie

Jan 1, 1970
0
Eeyore said:
Jamie wrote:




What an amazingly stupid comment !

How many op-amps run on 100mV ?

Graham
What a twit you are..!

why don't you include the text I replied to, you
british ignoramus.

I offer the most practical solution to get the
job done. You on the other hand would rather confuse
them with needless crap and keep a blog going so long that
the original content gets lost in bull shit like you post.

why don't you go back to doing what you're good at so we don't
have to be bothered seeing you here with your bull shit.

If you apply your self with the true skills you have, it should
relieve us from your pollution.

http://webpages.charter.net/jamie_5"
 
I have done what you intended, removing the magnet/coil
assembly from broken harddisks, and attaching 2 leds
antiparallel to the coil ends.
No need for rectifying, or boosting, just wiggle the coil
were it used to be, and the leds will light just fine.
Also interesting is, to shortcircuit the coil, and try to move
it, it acts as if inserted in syrup.
If you want more voltage from it use a small transformer.
using the primary as output, you get all the voltage you want.


Great! Simplifies things much. 2 LEDs... Much appreciated. Won't
have to go to the trouble of rectifying, or using a boost.

Yep, those neodymium magnets (neodymium-iron-boron?) from hard drives
are plenty strong.

Thanks again.

Michael
 

neon

Oct 21, 2006
1,325
Joined
Oct 21, 2006
Messages
1,325
On Dec 19, 2:11 pm, "ian field" <[email protected]>
wrote:
> "John Larkin" <[email protected]> wrote in message
>
> news:[email protected]...
>
> > On Fri, 19 Dec 2008 13:45:04 -0800 (PST), [email protected] 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

>
> > 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
If a transistor saturates you don't have any more audio .
 

neon

Oct 21, 2006
1,325
Joined
Oct 21, 2006
Messages
1,325
If it is for a clamp a 2n2907 will clamp down to MV in the reverse direction. but you need a force beta of 10.
 
E

Eeyore

Jan 1, 1970
0
Tim said:
The comment was for the OP.

I appreciate that. I was just adding my tuppence worth.

And I liked the semiconductor physics classes, too -- the only things
that kept me from diverting to a chip designer was that at the time
Portland State University thought "chip" meant "digital" and I'd already
decided I wanted to do control systems.

Universities can have some funny ideas !

Graham
 
J

Jasen Betts

Jan 1, 1970
0
No, I'm not kidding.

like this?
Version 4
SHEET 1 880 680
WIRE 352 16 240 16
WIRE 352 32 352 16
WIRE 176 80 96 80
WIRE 96 112 96 80
WIRE 240 112 240 16
WIRE 176 128 176 80
WIRE 208 128 176 128
WIRE 352 128 352 112
WIRE 208 160 192 160
WIRE 240 192 240 176
WIRE 352 192 240 192
WIRE 240 208 240 192
WIRE 96 224 96 192
WIRE 192 224 192 160
WIRE 192 224 96 224
FLAG 240 208 0
SYMBOL voltage 96 96 M0
WINDOW 3 8 106 Left 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value SINE(0 0.1 10)
SYMBOL Opamps\\LT1097 240 80 R0
SYMATTR InstName U1
SYMBOL res 336 16 R0
SYMATTR InstName R1
SYMATTR Value 10k
SYMBOL LED 336 128 R0
SYMATTR InstName D1
SYMATTR Value NSSW008CT-P1
TEXT 94 248 Left 0 !.tran 1
TEXT 208 296 Left 0 ;I'm kidding
 
J

Joerg

Jan 1, 1970
0
John said:
0.1 volts on the base of a bipolar wouldn't do much of anything.

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.

0.1V might be a challenge but I did get one to work at 0.2V without
resorting to legacy Ge devices. I used the snappiest JFET I could find.
You need all the gain you can get to make the things start up. Not ye
olde J309.

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

There are also zero volt threshold MOSFETs, Mouser has them (or at least
used to).

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

That really angered me as a kid. Almost every cookbook contained
oscillators with tunnel diodes and unijunction transistors and there was
no way for anyone to buy those unless your name was Rockefeller.
 
0.1V might be a challenge but I did get one to work at 0.2V without
resorting to legacy Ge devices. I used the snappiest JFET I could find.
You need all the gain you can get to make the things start up. Not ye
olde J309.


There are also zero volt threshold MOSFETs, Mouser has them (or at least
used to).


Ah, like these?
ALD110800/0900: Close-To-Zero Threshold MOSFETs
http://www.analogzone.com/acqp0620.htm

Learning something new every day...

Thanks,

Michael
 
W

whit3rd

Jan 1, 1970
0
0.1V might be a challenge but I did get one to work at 0.2V without
resorting to legacy Ge devices. I used the snappiest JFET I could find.

Selected parts, or single-source specials, are irritating.
Me, I'd think in terms of rewinding a vibrator coil.
Hey, solid state is nice, but it ain't everything!
 
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