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'[OT]: Re: [PIC]: Will an unprogrammed chip oscilla'
2002\06\14@195544 by

> > What take real skill is to make a 0 ohm resistor to within a 5%
> tollerance!
>
> Especially when you want to get a good symmetric bell-curve distribution
of
> the actual value ;)
>

Now Here's the real question:  if you have that bell curve, what do you do
with all the -ve resistance resistors?

Problem comes, though, when your resistor has to have 4 pins (supply leads)
to operate at the intended resistance ;)

--Brendan

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Brendan Moran <annirakBIGFOOT.COM> wrote:
> Now Here's the real question:  if you have that bell curve, what do you do
> with all the -ve resistance resistors?
>
> Problem comes, though, when your resistor has to have 4 pins (supply leads)
> to operate at the intended resistance ;)

We used to joke about that in college. A true "negative resistor" would
extract heat from the environment and produce a current flow. You'd have to
be careful not to let the leads short together, or a massive current would
flow and its temperature would quickly drop to absolute zero. You could get
some serious "freezer burns" that way :-).

Of course, there are devices that exhibit negative resistance, in the sense
that dV/dI is a negative value over certain parts of their operational
curves. They all still dissipate power in an absolute sense (V/I > 0),
however.

-- Dave Tweed

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At 08:38 AM 15/06/2002 -0700, you wrote:
>Brendan Moran <annirakBIGFOOT.COM> wrote:
> > Now Here's the real question:  if you have that bell curve, what do you do
> > with all the -ve resistance resistors?
> >
> > Problem comes, though, when your resistor has to have 4 pins (supply leads)
> > to operate at the intended resistance ;)
>
>We used to joke about that in college. A true "negative resistor" would
>extract heat from the environment and produce a current flow. You'd have to
>be careful not to let the leads short together, or a massive current would
>flow and its temperature would quickly drop to absolute zero. You could get
>some serious "freezer burns" that way :-).
>
>Of course, there are devices that exhibit negative resistance, in the sense
>that dV/dI is a negative value over certain parts of their operational
>curves. They all still dissipate power in an absolute sense (V/I > 0),
>however.

Yeah, an opamp and a few resistors would do it, that's what I meant by the
4-pin resistor.

--Brendan

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On Sat, 15 Jun 2002, Dave Tweed wrote:

>Brendan Moran <annirakBIGFOOT.COM> wrote:
>> Now Here's the real question:  if you have that bell curve, what do you do
>> with all the -ve resistance resistors?
>>
>> Problem comes, though, when your resistor has to have 4 pins (supply leads)
>> to operate at the intended resistance ;)
>
>We used to joke about that in college. A true "negative resistor" would
>extract heat from the environment and produce a current flow. You'd have to
>be careful not to let the leads short together, or a massive current would
>flow and its temperature would quickly drop to absolute zero. You could get
>some serious "freezer burns" that way :-).
>
>Of course, there are devices that exhibit negative resistance, in the sense
>that dV/dI is a negative value over certain parts of their operational
>curves. They all still dissipate power in an absolute sense (V/I > 0),
>however.

There were schemes of perpetuum mobile generators using carbon resistors
(old, noisy) and point rectifiers. According to some results I've seen
they work but don't try to run any loads on them ;-).

Peter

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