2-terminal negative resistance circuits

On a sunny day (Thu, 4 Jul 2019 02:29:38 -0800) it happened Robert Baer wrote in :

neon bulb

Most especially "Z" types.

Thanks.

Carbon arc Fluorescent tube Pretty much any discharge lamp Carbon pile with solenoid Nernst lamp

NT

Lambda diode

Cheers

Phil Hobbs

As a college ee project, I built a 2-terminal negative resistance box, with an opamp and a couple of 9 volt batteries. If you plug in a negative value for R into the common RC and RLC circuits, the math still works and the waveforms are radical.

I don't think my instructor understood it. They tended to not understand a lot of things that I did. That's another discussion.

Switching regulators, working into fixed loads, have negative input resistance, at DC anyway. Current draw goes up as you lower input voltage.

One might suspect that he understood it better than you did, and consequently wasn't giving you the sort of postive feedback that you seem expect from all your interactions.

Then again, neither do you, and you aren't great at discussion - if you aren't getting praised, you stop listening.

Physicist boss was using corundum as an abrasive on PZT8, while scooping some with an aluminum scoop, he did a measurement, and said hey, this has negative resistance. I didn't pay much attention, and not sure what he said is fact, but he was a very intelligent guy.

Mikek

Bill, you're getting awfully snarky in your old age.

Philips had a rather neat circuit for running a DC motor at constant speed even when the load varied - you measured the voltage across the motor, and the current through it, and made sure that the voltage across the motor was equal to the back-emf that you wanted (and the rotation speed) plus the vo ltage drop in the motor windings.

I used it once, and it worked fine, but you did have to roll off the the ne gative resistance at higher frequencies.

He should design something. He might feel better.

Lambda diode (e.g. two JFETs).

I like to think of myself as more of boojum.

I feel fine. I've even designed some stuff recently - though the NSW IEEE July Newsletter is not the kind of electronic design that John Larkin would like us to think that he is thinking of.

Coming home from an excellent dinner in a three star restaurant is an even better way of getting to feel fine, though it doesn't seem to make me any more tolerant of half-baked opinions.

Parallel such a box with a variable resistor, and make a quartz crystal tester (which starts from white noise when the 'gain' reaches Barkhausen's criterion).

I'd be thinking of using a LM13700 instead of op amp, though. Transconductance is a the property you want, it just takes a bias resistor or two.

Not possible. Either sentence.

Oh. Sorry.

I used a slow opamp, 709 or maybe 741 by then, so it was only good to

How would you make a 2-terminal negative resistor with an LM13700?

Maybe you did, but I see by your responses to John's posts, you are very jealous of what he does.

Mikek