2-terminal negative resistance circuits

On Thursday, July 4, 2019 at 4:16:39 PM UTC-7, John Larkin wrote: ood for testing crystals.

Positive input to terminal 1, negative input to terminal 2, and the output is a current source proportional to the voltage difference; wire that to terminal 1. Either midpoint/ground terminal 2, or (if you want to get fancy and have more compliance range) use the second section amplifier with inverted input polarities and wire its output to terminal 2.

inputs won't like +/-9V range, but maybe you can power it with a couple of lithium cells and get by. One or two resistors, to bias the amplifier(s) is the rest of the part count. One chip, two resistors, two batteries. An Altoids box and some black paint and voila!

Reply to
whit3rd
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Did he ever finish that world shaking low distortion oscillator he started about a decade ago?

Reply to
Michael Terrell

I asdmire his capacity to get paid for it, but it is bit irritating to listen to him congratulate himself for "innovative" stuff that we were doing back in the late 1980's.

He's got faster components to play with, so in one sense he's doing it better, but we worked out a few tricks that he doesn't seem to have taken on board.

He has got himself a fairly sweet gig - for him. It's not one that would suit me, so I'm probably not actually jealous.

--
Bill Sloman, Sydney
Reply to
Bill Sloman

d about a decade ago?

If the low distortion oscillator had been world-shakng, it might have shake n loose a few potential customers.

The schematics are complete enough, and I started putting them into KiCad a few years ago, with the idea of turning them into a printed circuit layout which I could get made and stuffed, and test, but in the total absence of any potential customers I've never got on with it.

--
Bill Sloman, Sydney
Reply to
Bill Sloman

Krw's grasp of possibilities is as feeble as the rest of his grasp of reality.

--
Bill Sloman, Sydney
Reply to
Bill Sloman

Or indeed one fet and one bjt.

piglet

Reply to
piglet

Please what is meant by "Z type" ?

piglet

Reply to
piglet

Like

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Nice circuit! Why isn't that in the AoE? (at least not in the index)

Arie

Reply to
Arie de Muynck

Nice idea, Arie. What can you do with it?

We like depletion devices, whether JFETs or MOSFETs. But the -Vgs curve isn't specified or very dependable.

--
 Thanks, 
    - Win
Reply to
Winfield Hill

On a sunny day (5 Jul 2019 02:30:02 -0700) it happened Winfield Hill wrote in :

One trannny: 0 V + | ___ |________ | | | R1 | | | |/ c | |---- -| | | |\|e R3

--- | | \ / > |----

--- LED R2 | | -------- | 0 V -

Z1 1.5V LED R1 10k R2 1k R3 10k

At low voltages circuit conducts a lot via transistor and R2, tranny basically shorts R3.

When V goes high at some point (about 10 V) emitter is lifted bove VZ1 - Vbe, Ic drops to zero, only current left via R1 and LED plus current through R2 + R3.

Reply to
Jan Panteltje

Cross-coupled transistor pair.

Pere

Reply to
o pere o

Dynamic load for power supplies. I had a problem with leaking schottky's in a dual input PSU (PoE and 24Vac input circuits). When the sun burned on the equipment (80C inside), the leakage from the isolation diode to the PoE circuits caused lockup, PoE would not start in some circumstances. Solved it with a more complex circuit, this negative resistor would have worked fine. The Vgs spread would have been tolerable but maybe the JFET + BJE circuit would have been more reproducable. Time for some LTspicing...

Arie

Reply to
Arie de Muynck

Could do watch crystals. I also have a glass valve type encased crystal that's 5 or 6 kHz.

NT

Reply to
tabbypurr

Very nice idea too. Reminds me of the SOA foldback in PSU and audio output amplifier circuits. Problem for me would be the high remaining current through R3, there is no current gain in that path like with the BJE + JFET circuit. I need a high (inverse) current ratio between lo and high voltage load.

BTW - running out of pencils?

Arie

Reply to
Arie de Muynck

make stable things unstable. Improve Q.

NT

Reply to
tabbypurr

On a sunny day (Fri, 5 Jul 2019 13:22:44 +0200) it happened Arie de Muynck wrote in :

Yes, but then again an Esaki (tunnel) diode also has high remaining current, it just decreases a bit at some point. He did not ask for 'linear' :-)

No, but this circuit is so simple that ASCII art will do. It also better preserved as web links may come and go as servers do.

Reply to
Jan Panteltje

That's sure a collectors item. Big flex mode slab of quartz, likely. I wonder if the motion would be visible.

I thought this was beautiful, a custom 40 MHz AT cut sealed in vacuum.

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The '60' on the bottom is the turning point temperature.

I used to design my own OCXOs but they have gotten very good and very cheap lately.

--
John Larkin   Highland Technology, Inc   trk 

jlarkin att highlandtechnology dott com 
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Reply to
John Larkin

On a sunny day (Fri, 5 Jul 2019 11:34:31 -0800) it happened Robert Baer wrote in :

After posting that neon bulb remark I realized it is not negative resistance AFAIK, as its resistance suddenly DECREASES when the voltage across it rises. The tunnel diode exhibits true negative resistance, as do some transistor circuits discussed elsewhere.

I dunno, have only used chili lately.

Reply to
Jan Panteltje

Neon bulb more like it; not a circuit but is (mostly) N-type. Perhaps with some care, one can extract the negative resistance avalanche-type characteristics.

In any case, is there a SPICE model?

Reply to
Robert Baer

Not circuits,not SPICE models.

Reply to
Robert Baer

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