Re: negative resistor

On Sat, 07 Oct 2006 23:04:21 -0700, Tim Wescott <tim@xxxxxxxxxxxxxxxx>
wrote:

John Larkin wrote:

On 7 Oct 2006 16:46:57 -0700, "STUARTe" <jabluvs269@xxxxxxxxxxx>
wrote:


if you look at the voltage current relationship at the input side of a
voltage regulator, you'll note that it acts like a negative resistor.


Only a switcher, not a linear regulator.


as the voltage source increases, the current decreases.
my question is, could you get a super conducting (zero resistance)
element by putting a resistor in series with the negative resistor?


You can get as close to zero resistance as tolerances allow, but it's
not a superconductor, it's just a synthesized zero resistance between
two nodes, and it needs a power supply to keep working.

You can do some fun experiments with a 2-terminal negative resistor.
All the normal circuit equations work, but with unusual results, like
voltage dividers with gain and stuff.

John

For a while one of the useful amplifying elements at microwaves was the
tunnel diode. One segment of the tunnel diode's V-I curve has a
pronounced negative slope, so you can use it for building amplifiers and
oscillators.

Better microwave transistors pretty much killed off the tunnel diode,
but the Gunn diode (also a negative resistance device in it's own
peculiar way) is still a useful critter at 10GHz, where transistors tend
to be too slow.

For power at microwave, IMPATTs surpassed GUNNs and transistors.

The Phoenix Missile for example, used phase locked GUNNs for the LO
and TO and then a three-stage "amplifier" (really injected-locked
oscillators) using IMPATTs.

The first stage used a single IMPATT; the second, three IMPATTS; the
third had sixteen IMPATTs in a cavity combiner. Twenty-five+ years
ago when we were developing this, getting sixteen nearly matched
diodes was a real challenge.

.

Relevant Pages

  • Re: negative resistor
    ... you'll note that it acts like a negative resistor. ... Better microwave transistors pretty much killed off the tunnel diode, but the Gunn diode is still a useful critter at 10GHz, where transistors tend to be too slow. ... IMPATTs surpassed GUNNs and transistors. ... used phase locked GUNNs for the LO ...
    (sci.electronics.design)
  • Re: negative resistor
    ... voltage regulator, you'll note that it acts like a negative resistor. ... You can get as close to zero resistance as tolerances allow, ... Better microwave transistors pretty much killed off the tunnel diode, ...
    (sci.electronics.design)
  • Re: negative resistor
    ... voltage regulator, you'll note that it acts like a negative resistor. ... You can get as close to zero resistance as tolerances allow, ... Better microwave transistors pretty much killed off the tunnel diode, but the Gunn diode is still a useful critter at 10GHz, where transistors tend to be too slow. ...
    (sci.electronics.design)
  • Re: negative resistor
    ... you'll note that it acts like a negative resistor. ... as the voltage source increases, ... You already have that situation at the voltage regulator output. ... magnetic fields, dissipate zero power, etc.... ...
    (sci.electronics.design)
  • Re: negative resistor
    ... voltage regulator, you'll note that it acts like a negative resistor. ... the current decreases. ... simple-minded word reasoning devoid of the slightest underlying reality. ...
    (sci.electronics.design)